The 1975 revision of the World Health Organization (WHO) series of statistical classifications, which was expanded for North American use into the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). One often finds reference to use of ICD-9 as the disease classification system being employed in clinical settings, research, and reimbursement systems in the United States. This is incorrect; the system being used is ICD-9-CM, except in references to the international exchange of statistical information at the national level.