An outbreak of hepatitis A in a neonatal intensive care unit was apparently attributable to blood transfusion. Several infants received aliquots from a single unit of packed red blood cells donated by an individual who subsequently became ill with hepatitis A. Although none of the infants became symptomatic, there was serologic evidence of recent exposure in four. Several staff and family members exposed to these infants became symptomatic. An adult patient who received platelets from this same unit developed elevated liver enzymes and his wife also showed serologic evidence of hepatitis A. These are the first reported cases of hepatitis A associated with a blood transfusion since implementation of alanine aminotransferase testing.