A 13-year-old boy who had had recurrent photosensitive skin reactions due to erythropoietic protoporphyria from 18 months of age, suddenly developed rapidly progressive hepatic failure with increasing cholestatic jaundice and variceal bleeding. Liver biopsy confirmed extensive protoporphyrin deposition with cirrhosis, and so orthotopic liver transplantation was performed. Postoperatively his skin rash settled within 72 hr, and in spite of subsequent exposure to the sun he has had no further skin reaction or blistering, although he does still have some itching. He made a good recovery and was able to return to school within six months of operation. Prior to liver transplantation, the hepatic ferrochelatase activity was reduced to only 0.81 nmol zinc-protoporphyrin formed/mg protein/hr (controls 3.30 +/- 1.00 nmol zinc-protoporphyrin formed/mg protein/hr, while the red cell protoporphyrin level was markedly elevated at 188 mumol/L red cells (normal less than 1.6 mumol/L red cells). The free plasma porphyrin level of 0.95 mumol/L (normal less than 0.02 mumol/L), and the urinary and fecal porphyrin levels were also raised. Following liver grafting these elevated porphyrin levels fell rapidly, with the red cell protoporphyrin level dropping to 10% of its preoperative value, and the rest returning to virtually normal within three months of operation.