Deaths from pregnancy complications remain an important public health concern. Nationally, two systems collect information on the number of deaths and characteristics of the women who died from complications of pregnancy. The Centers for Disease Control and Prevention's (CDC) National Center for Health Statistics (NCHS) reports maternal mortality through the National Vital Statistics System (NVSS); CDC National Center for Chronic Disease Prevention and Health Promotion's Pregnancy Mortality Surveillance System (PMSS) conducts epidemiological surveillance of pregnancy-related deaths. The numbers of deaths reported by these two systems have differed over the past two decades; our objective was to determine the magnitude and nature of these differences. For 1995-97, we compared maternal deaths in the NVSS with pregnancy-related deaths in PMSS for the 50 States, Washington DC and New York City. Pregnancy-related deaths whose underlying cause was assigned to ICD-9 codes 630-676 by NVSS were classified as maternal deaths; those coded outside 630-676 were not. There were 1387 pregnancy-related deaths in PMSS and 898 maternal deaths in the NVSS; 54% of these deaths were reported in both systems, 40% in PMSS only, and 6% in NVSS only. Pregnancy-related deaths due to haemorrhage, embolism, and hypertensive complications of pregnancy were proportionately more often identified by NVSS as maternal deaths than those from cardiovascular complications, medical conditions or infection. From the 1471 unduplicated deaths classified as maternal or pregnancy-related from either reporting system, we estimated a combined pregnancy-related mortality ratio of 12.6/100,000 live births for 1995-97, compared with 11.9 for PMSS only and 7.5 for NVSS only. The identification and classification of these events is dependent on the provision of complete and accurate cause-of-death information on death certificates. Changes in the guidelines for coding maternal deaths under ICD-10 may change the relationship in the number of deaths resulting from pregnancy reported by these two systems.