The New York State Perinatal Hepatitis B Prevention Program was implemented in New York State (excluding New York City) as a surveillance and control program in 1988. This report describes and evaluates the program and provides data from 1991 regarding hepatitis B surface antigen (HBsAg)-positive mothers and their infants' subsequent hepatitis B vaccination. The program was created using multiple existing surveillance and data collection systems. Completeness of case-ascertainment was estimated by means of the Chandra Sekar-Deming method (J Am Stat Assoc 1949; 44:101-15). An audit of hospital medical records and follow-up by local health departments were used to validate reporting accuracy. Of 158,273 live births in 1991, 363 (0.2%) were born to confirmed HBsAg-positive mothers. Estimated completeness of case-ascertainment was 96%. Thirty-five percent of HBsAg-positive mothers did not report risk factors for hepatitis B, confirming the need for universal testing. Of the infants, 83% received hepatitis B immune globulin and three doses of vaccine within one year of birth. By using existing data collection systems, the program was established quickly, and start-up funding and training requirements were simplified. Multiple reporting increased case-ascertainment to almost 100%. The program effectively identifies and ensures prompt vaccination of infants born to HBsAg-positive mothers.