Erythropoietic protoporphyria, caused by an inherited deficiency of ferrochelatase, results in increased free protoporphyrin concentrations in erythrocytes and plasma. Cutaneous photosensitivity is the primary clinical manifestation, but in some patients, protoporphyrin accumulation in the liver may lead to fatal hepatic failure. No treatment exists for this lethal complication. We report the case of a patient with erythropoietic protoporphyria and abnormal results of liver function tests in whom oral iron therapy led to a substantial decrease in free erythrocyte and stool protoporphyrin levels with return of liver function to normal. Iron therapy should be considered for preventing potentially fatal hepatic failure in patients with erythropoietic protoporphyria.