International Classification of Diseases (ICD) A medical code set maintained by the World Health Organization (WHO). The primary purpose of this code set was to classify causes of death. A US extension of this coding system, maintained by the NCHS within the CDC, identifies morbidity factors, or diagnoses. The ICD-9-CM codes have been selected for use in the HIPAA transactions. How the abbreviation ICDnCM/PCS breaks down: ICD = International Classification of Diseases n = revision number CM = Clinical Modification PCS = Procedure Coding System Related Terms: Clinical Modification ; International Classification of Diseases, Revision 9, Clinical Modification; National Center for Health Statistics ; Procedure Coding System ; World Health Organization; Legislation Files Containing This Term: legislation/45CFR-162.1002.html