To assess the usefulness of vital statistics and surveillance for monitoring abortion mortality, the authors compared data from two systems of classification: 1) deaths classified according to the underlying cause by the National Center for Health Statistics (NCHS) under the International Classification of Disease, Adapted (ICDA) code numbers 640-645 (abortion) for 1972-1975; and 2) abortion-related deaths reported to the Center for Disease Control (CDC) through its epidemiologic surveillance of abortion mortality for the same years. Vital statistics classifications dealing with the underlying cause of death are based on criteria defined by ICDA guidelines applied to all available information listed on death certificates, and exclude some deaths classified as abortion-related by CDC. Surveillance classifications are based on broader criteria developed by CDC for expanded data gathered by individual case investigation. Results showed that the surveillance techniques had identified more deaths as abortion-related and had resolved more cases into the specific abortion categories of legal, illegal, and spontaneous than vital statistics tabulations based on death certificates. The authors estimate that the surveillance system alone reported 88% of all abortion-related deaths, the vital statistics system 52%, and the two systems combined a total of 94%. Inadequate physician documentation on the death certificate was the primary reason vital statistics data contained a smaller number of reported abortion deaths than surveillance data.