The OC-MEDS Data Dictionary (OCEMS Policy #300.31) provides comprehensive data standards and reporting conditions for patient care incidents conducted by EMS personnel and provider agencies which include Ambulance Companies, Fire Departments, and Hospitals.  The main document and all supporting attachments are available below for viewing and download. Past versions of this policy are also available for archival reference.

Upcoming - OC-MEDS Data Dictionary - v3.5.1 (Effective Date 4/1/2026)

• OCEMS Policy 300.31 - Change Log (v3.5 - 04/01/2026)
• OCEMS Policy 300.31 - OC-MEDS Data Dictionary (v3.5 - 04/01/2026)
• OCEMS Policy 300.31 - Attachment 1 - Data Element List -  (v3.5 - 04/01/2026)
• OCEMS Policy 300.31 - Attachment 2 - Facilities List - (v3.5 - 04/01/2026)
• OCEMS Policy 300.31 - Attachment 3 - EMS Provider Agencies - (v3.5 - 04/01/2026)
• OCEMS Policy 300.31 - Attachment 4 - Procedures (eProcedures.03) - (v3.5 - 04/01/2026)
• OCEMS Policy 300.31 - Attachment 5 - Medications Given (eMedications.03) - (v3.5 - 04/01/2026)
• OCEMS Policy 300.31 - Attachment 6 - Cause of Injury (eInjury.01)- (v3.5 - 04/01/2026)
• OCEMS Policy 300.31 - Attachment 7 - Disposition (itDisposition.112) - (v3.5 - 04/01/2024)
• OCEMS Policy 300.31 - Attachment 8 - Symptoms (eSituation.09 & 10) - (v3.5 - 04/01/2024)
• OCEMS Policy 300.31 - Attachment 9 - Impressions (eSituation.11 & 12) - (v3.5 - 04/01/2026)
• OCEMS Policy 300.31 - Attachment 10 - Incident Location Type (eScene.09) - (v3.5 - 04/01/2024)
• OCEMS Policy 300.31 - Attachment 11 - Medication Allergies (eHistory.06) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 12 - Environmental Allergies (eHistory.07) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 13 - Medical Surgical History (eHistory.08) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 14 - Current Medication (eHistory.12) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 15 - Approved Abbreviations (eNarrative.01) - (v3.5 - 05/07/2024)
• OCEMS Policy 300.31 - Attachment 16 - OC Fire Districts (itScene.025) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 17 - Orange County EOAs - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 18 - Reporting Conditions / Validation Rules - (v3.5 - 04/01/2024)

Current - OC-MEDS Data Dictionary - v3.5 (Effective Date: 4/1/2025)

• OCEMS Policy 300.31 - Change Log (v3.5 - 10/01/2024)
• OCEMS Policy 300.31 - OC-MEDS Data Dictionary (v3.5 - 04/01/2024)
• OCEMS Policy 300.31 - Attachment 1 - Data Element List -  (v3.5 - 04/01/2024)
• OCEMS Policy 300.31 - Attachment 2 - Facilities List - (v3.5 - 04/01/2025)
• OCEMS Policy 300.31 - Attachment 3 - EMS Provider Agencies - (v3.5 - 10/01/2024)
• OCEMS Policy 300.31 - Attachment 4 - Procedures (eProcedures.03) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 5 - Medications Given (eMedications.03) - (v3.5 - 04/01/2024)
• OCEMS Policy 300.31 - Attachment 6 - Cause of Injury (eInjury.01)- (v3.5 - 04/01/2024)
• OCEMS Policy 300.31 - Attachment 7 - Disposition (itDisposition.112) - (v3.5 - 04/01/2024)
• OCEMS Policy 300.31 - Attachment 8 - Symptoms (eSituation.09 & 10) - (v3.5 - 04/01/2024)
• OCEMS Policy 300.31 - Attachment 9 - Impressions (eSituation.11 & 12) - (v3.5 - 04/01/2024)
• OCEMS Policy 300.31 - Attachment 10 - Incident Location Type (eScene.09) - (v3.5 - 04/01/2024)
• OCEMS Policy 300.31 - Attachment 11 - Medication Allergies (eHistory.06) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 12 - Environmental Allergies (eHistory.07) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 13 - Medical Surgical History (eHistory.08) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 14 - Current Medication (eHistory.12) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 15 - Approved Abbreviations (eNarrative.01) - (v3.5 - 05/07/2024)
• OCEMS Policy 300.31 - Attachment 16 - OC Fire Districts (itScene.025) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 17 - Orange County EOAs - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 18 - Reporting Conditions / Validation Rules - (v3.5 - 04/01/2024)

Resources - Letters and Memos

• OC-MEDS Notice - Crew Member Meds & Procs - Mar 2026
• OCEMS Letter #5605 - OC-MEDS PCRS Update -Transition to NEMSIS v3.5.1
• NEMSIS Critical Patch - CEMSIS Update Letter (05/29/2025)
• OCEMS Letter #5434 - OC-MEDS PCRS Updates (05/06/2025)
• OC-MEDS Data Dictionary v3.5 Technical Summary / Change Log (06/30/2023)
• California EMS Authority - NEMSIS v3.5 Transition Reminder Memo (10/11/2023)
• OCEMS Letter #4722 - NEMSIS v3.5 Transition - Final Implementation Guidance (09/01/2023)
• OCEMS Letter #4651 - Data Dictionary Finalized / NEMSIS v3.5 Transition Update (07/05/2023)
• OCEMS Letter #4638 - NEMSIS v3.5 Transition Update #3 (06/08/2023)
• OCEMS Letter #4580 - NEMSIS v3.5 Transition Update (04/04/2023)
• California EMS Authority - CEMSIS Update Memo (02/22/2023)
• OCEMS Letter #4522 - NEMSIS v3.5 Transition Plan (01/03/2023)

Archived - OC-MEDS Data Dictionary - v3.5 

• OCEMS Policy 300.31 - Change Log (v3.5 - 04/01/2024)
• OCEMS Policy 300.31 - OC-MEDS Data Dictionary (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 1 - Data Element List -  (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 2 - Facilities List - (v3.5 - 10/01/2024)
• OCEMS Policy 300.31 - Attachment 2 - Facilities List - (v3.5 - 04/01/2024)
• OCEMS Policy 300.31 - Attachment 2 - Facilities List - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 3 - EMS Provider Agencies - (v3.5 - 04/01/2024)
• OCEMS Policy 300.31 - Attachment 3 - EMS Provider Agencies - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 5 - Medications Given (eMedications.03) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 6 - Cause of Injury (eInjury.01)- (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 7 - Disposition (itDisposition.112) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 8 - Symptoms (eSituation.09 & 10) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 9 - Impressions (eSituation.11 & 12) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 10 - Incident Location Type (eScene.09) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 15 - Approved Abbreviations (eNarrative.01) - (v3.5 - 10/01/2023)
• OCEMS Policy 300.31 - Attachment 18 - Reporting Conditions / Validation Rules - (v3.5 - 10/01/2023)

Archived - OC-MEDS Data Dictionary - v1.3 (Effective Date: 06/01/2019) 

• OCEMS Policy 300.31 - OC-MEDS Data Dictionary (v1.3 - 6/01/2019)
• OCEMS Policy 300.31 - OC-MEDS Data Dictionary (Main Document) v1.3 - 06/01/2019)
• OCEMS Policy 300.31 - Attachment 1 - Orange County Facilities Data List (v1.7 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 2 - EMS Provider Agency Data List (v1.3 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 3 - eHistory.12 Data List (v1.2 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 4 - Orange County Cities and Places GNIS Code List (v1.0 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 5 - eHistory.08 Data List (v1.0 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 6 - eProcedures.03 Data List (v1.5 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 7 - eScene.09 Data List (v1.5 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 8 - eInjury.01 Data List (v1.3 -06-01-2019)
• OCEMS Policy 300.31 - Attachment 9 - eMedications.03 Data List (v1.8 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 10 - Orange County Fire District Numbers Data List (v1.0 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 11 - Orange County EOA Data List (v.1.0 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 12 - eSituation.11 and eSituation.12 Data List (v1.8 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 13 - eSituation.09 Data List (v1.1 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 14 - eHisotry.06 Data List (v1.1 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 15 - eHistory.07 Data List (v1.0 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 16 - eNarrative.01 - Approved Abbreviations (v1.0 - 06-01-2019)
• OCEMS Policy 300.31 - Attachment 17 - eDisposition.12 - Field Value Definitions (v1.1 - 06-01-2019)

Archived - OC-MEDS Data Dictionary Change Log - (06/01/2019)

• OC-MEDS Data Dictionary - Change Notification (June 2019)
• OC-MEDS Data Dictionary - Change Log Summary (06-01-2019)

Archived - OC-MEDS Data Dictionary - v1.2 

• OCEMS Policy 300.31 - OC-MEDS Data Dictionary (Data Element List and Table of Contents)
• OCEMS Policy 300.31 - OC-MEDS Data Dictionary (Main Document)
• OCEMS Policy 300.31 - Attachment 1 - Orange County Facilities Data List (v1.6 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 2 - EMS Provider Agency Data List (v1.2 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 3 - eHistory.12 Data List (v1.2 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 4 - Orange County Cities and Places GNIS Code List (v1.0 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 5 - eHistory.08 Data List (v1.0 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 6 - eProcedures.03 Data List (v1.5 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 7 - eScene.09 Data List (v1.5 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 8 - eInjury.01 Data List (v1.3 -04-01-2018)
• OCEMS Policy 300.31 - Attachment 9 - eMedications.03 Data List (v1.7 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 10 - Orange County Fire District Numbers Data List (v1.0 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 11 - Orange County EOA Data List (v.1.0 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 12 - eSituation.11 and eSituation.12 Data List (v1.7 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 13 - eSituation.09 Data List (v1.0 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 14 - eHisotry.06 Data List (v1.1 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 15 - eHistory.07 Data List (v1.0 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 16 - eNarrative.01 - Approved Abbreviations (v1.0 - 04-01-2018)
• OCEMS Policy 300.31 - Attachment 17 - eDisposition.12 - Field Value Definitions (v1.0 - 04-01-2018)

Archived - OC-MEDS Data Dictionary Change Log - (04/01/2018)

• OC-MEDS Data Dictionary - Change Log Summary (04-01-2018)
• Attachment 1 - Orange County Facilities Data List (Change Log - 04-01-2018)
• Attachment 2 - EMS Provider Agency Data List (Change Log - 04-01-2018)
• Attachment 6 - eProcedures.03 Data List (Change Log - 04-01-2018)
• Attachment 9 - eMedications.03 Data List (Change Log - 04-01-2018) 

Archived - OC-MEDS Data Dictionary - v1.1 

• OCEMS Policy 300.31 - OC-MEDS Data Dictionary (Data Element List and Table of Contents)
• OCEMS Policy 300.31 - OC-MEDS Data Dictionary (Main Document)
• OCEMS Policy 300.31 - Attachment 1 - Orange County Facilities Data List (v1.5 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 2 - EMS Provider Agency Data List (v1.1 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 3 - eHistory.12 Data List (v1.2 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 4 - Orange County Cities and Places GNIS Code List (v1.0 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 5 - eHistory.08 Data List (v1.0 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 6 - eProcedures.03 Data List (v1.5 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 7 - eScene.09 Data List (v1.5 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 8 - eInjury.01 Data List (v1.3 -04-01-2017)
• OCEMS Policy 300.31 - Attachment 9 - eMedications.03 Data List (v1.7 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 10 - Orange County Fire District Numbers Data List (v1.0 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 11 - Orange County EOA Data List (v.1.0 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 12 - eSituation.11 and eSituation.12 Data List (v1.7 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 13 - eSituation.09 Data List (v1.0 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 14 - eHisotry.06 Data List (v1.1 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 15 - eHistory.07 Data List (v1.0 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 16 - eNarrative.01 - Approved Abbreviations (v1.0 - 04-01-2017)
• OCEMS Policy 300.31 - Attachment 17 - eDisposition.12 - Field Value Definitions (v1.0 - 04-01-2017)

Archived - OC-MEDS Data Dictionary Change Log - (04/01/2017)

• OC-MEDS Data Dictionary - Change Log Summary (04-01-2017)
• Attachment 1 - Orange County Facilities Data List (Change Log - 04-01-2017)
• Attachment 3 - eHistory.12 Data List (Change Log - 04-01-2017)
• Attachment 7 - eScene.09 Data List (Change Log - 04-01-2017)
• Attachment 9 - eMedications.03 Data List (Change Log - 04-01-2017)
• Attachment 12 - eSituation.11 and eSituation.12 Data List (Change Log - 04-01-2017)

Archived - OC-MEDS Data Dictionary - v1.0 

• OCEMS Policy 300.31 - OC-MEDS Data Dictionary (Data Element List and Table of Contents)
• OCEMS Policy 300.31 - OC-MEDS Data Dictionary (Main Document)
• OCEMS Policy 300.31 - Attachment 1 - Orange County Facilities Data List (v1.4 - 10-01-2016)
• OCEMS Policy 300.31 - Attachment 2 - EMS Provider Agency Data List (v1.1 - 10-01-2016)
• OCEMS Policy 300.31 - Attachment 3 - eHistory.12 Data List (v1.1 - 10-01-2016)
• OCEMS Policy 300.31 - Attachment 4 - Orange County Cities and Places GNIS Code List (v1.0 - 10-01-2016)
• OCEMS Policy 300.31 - Attachment 5 - eHistory.08 Data List (v1.0 - 10-01-2016)
• OCEMS Policy 300.31 - Attachment 6 - eProcedures.03 Data List (v1.5 - 10-01-2016)
• OCEMS Policy 300.31 - Attachment 7 - eScene.09 Data List (v1.4 - 10-01-2016)
• OCEMS Policy 300.31 - Attachment 8 - eInjury.01 Data List (v1.3 -10-01-2016)
• OCEMS Policy 300.31 - Attachment 9 - eMedications.03 Data List (v1.6 - 10-01-2016)
• OCEMS Policy 300.31 - Attachment 10 - Orange County Fire District Numbers Data List (v1.0 - 10-01-2016)
• OCEMS Policy 300.31 - Attachment 11 - Orange County EOA Data List (v.1.0 - 10-01-2016)
• OCEMS Policy 300.31 - Attachment 12 - eSituation.11 and eSituation.12 Data List (v1.6 - 10-01-2016)
• OCEMS Policy 300.31 - Attachment 13 - eSituation.09 Data List (v1.0 - 10-01-2016)
• OCEMS Policy 300.31 - Attachment 14 - eHisotry.06 Data List (v1.1 - 10-01-2016)
• OCEMS Policy 300.31 - Attachment 15 - eHistory.07 Data List (v1.0 - 10-01-2016)

Archived - OC-MEDS Data Dictionary Change Log - (10/01/2016)

• OC-MEDS Data Dictionary - Change Log Summary (10-01-2016)
• OC-MEDS Data Dictionary - Main Document (Redline Version)
• Attachment 1 - Orange County Facilities Data List (Change Log - 10-01-2016)
• Attachment 6 - eProcedures.03 Data List (Change Log - 10-01-2016)
• Attachment 7 - eScene.09 Data List (Change Log - 10-01-2016)
• Attachment 8 - eInjury.01 Data List (Change Log - 10-01-2016)
• Attachment 9 - eMedications.03 Data List (Change Log - 10-01-2016)
• Attachment 12 - eSituation.11 and eSituation.12 Data List (Change Log - 10-01-2016)