A 24-year-old man who had been a drug addict for years, was admitted to hospital having been unconscious for several hours after injecting an overdose of heroin. He was in acute renal failure with extensive swelling of soft tissues of the right upper leg and right buttock without external signs of injury. The swelling rapidly extended to both right limbs, trunk and external genitalia. The clinical suspicion of rhabdomyolysis was confirmed by a high level of serum myoglobin (1570 mg/ml), and in a gluteus maximus muscle biopsy. The acute renal failure caused by the rhabdomyolysis was reversible after a short period of haemodialysis and, after decompression fasciotomy of the affected muscles, there were no severe sequelae. In view of the good prognosis with early diagnosis an exact clinical examination (observation of soft tissue swelling and dark urine) is of great importance in case of heroin addiction and/or poisoning.