The International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) is based on the World Health Organization's Ninth Revision, International Classification of Diseases (ICD-9). ICD-9-CM is the official system of assigning codes to diagnoses and procedures associated with hospital utilization in the United States. The ICD-9 was used to code and classify mortality data from death certificates until 1999, when use of ICD-10 for mortality coding started.

The ICD-9-CM consists of:

• a tabular list containing a numerical list of the disease code numbers in tabular form;
• an alphabetical index to the disease entries; and
• a classification system for surgical, diagnostic, and therapeutic procedures (alphabetic index and tabular list).