In the United States, an estimated 24,000 women with hepatitis B virus (HBV) infection give birth each year. To prevent mother-to-child HBV transmission, the Advisory Committee on Immunization Practices (ACIP) recommends administering postexposure prophylaxis of hepatitis B vaccine (HepB) and hepatitis B immune globulin (HBIG) to infants born to HBV-infected women within 12 hours of delivery, followed by completion of the HepB series. In 1990, CDC established a national Perinatal Hepatitis B Prevention Program (PHBPP) to support federal immunization program grantees in performing this ACIP-recommended case management of infants born to HBV-infected women. Perinatal HBV infections currently are reported by state and local health departments to CDC through two parallel processes: by immunization programs as part of federal program grant reporting requirements and by communicable disease surveillance units as part of the National Notifiable Diseases Surveillance System (NNDSS). A review of perinatal HBV infection reporting for infants born in 2005 identified 68 cases reported by immunization programs and 47 cases reported by communicable disease surveillance units, resulting in a total of 73 unique cases, 42 (58%) of which were reported by both systems. Following investigation, data reconciliation, and additional NNDSS reporting, 78 unique cases were identified, 63 (84%) of which were reported by both systems. Improved information-sharing between immunization programs and communicable disease surveillance units of health departments is essential to ensure more complete identification, case management, and quantification of perinatal HBV infections. Accuracy and completeness of perinatal HBV infection reporting can help ensure and measure progress toward elimination of HBV transmission in the United States.