Erythropoietic protoporphyria is an inherited disorder characterized biochemically by a deficiency of ferrochelatase, the enzyme that catalyzes the incorporation of ferrous iron into protoporphyrin to form heme. We describe a patient who illustrates the unpredictability of the course of liver disease in erythropoietic protoporphyria. She remained stable for several years after her first evidence of liver function abnormalities. Then, in a period of weeks, hepatic failure developed and she died. Findings of serial liver biopsy specimens showed extensive hepatocellular degeneration and inflammation that appeared in a 10-day period. The factors that cause this rapid deterioration in hepatic function remain unknown. Reported cases of fatal hepatic failure in patients with erythropoietic protoporphyria are reviewed.