We describe a neonate with hemolytic disease of the newborn in whom a photosensitivity eruption developed during phototherapy for treatment of hyperbilirubinemia. Free erythrocyte protoporphyrin and zinc protoporphyrin levels were markedly elevated during the neonatal period. Porphyrin levels were normal at 19 weeks of age. The infant had residual skin atrophy and showed clinical and radiologic evidence of kernicterus. The pathogenesis of transient porphyrinemia associated with hemolytic disease of the newborn is unclear.