24 days after starting treatment of psoriasis with fumaric acid derivatives (0.8-1.0 g orally, plus unknown quantities locally) a 21-year-old woman developed acute oliguric renal failure with a rise of serum creatinine levels to 1094 mumol/l (12.4 mg/dl). Deterioration of renal function had been preceded by severe abdominal symptoms with nausea, vomiting and colicky pain. On admission to hospital she was dehydrated with hyponatraemia and hypokalaemia. There was glomerular microhaematuria, increased excretion of renal epithelia, and tubular proteinuria. Renal biopsy demonstrated acute tubular damage with vacuolization of proximal epithelia, dilated tubules and scattered necroses. After intermittent haemodialysis (13 courses over two weeks) renal function gradually recovered, as demonstrated at a follow-up examination four months after discharge.