Eight hours following tympanoplasty performed under general anaesthesia (sodium pentothal and trichloroethylene), a 30 year old male complained of muscular weakness and dark coloured urine. Urinalysis revealed myoglobin pigment. A rise in BUN (47mg%), serum creatinine (5.7mg%), creatinine phosphokinase (15,500 U/L) and CPK-MB fraction (4690 U/L) was noticed 36 hrs later. The patient developed acute renal failure, and recovered after haemodialysis. From a history of use of succinylcholine as a muscle relaxant during operation, myoglobinuria appears to be secondary to muscle damage caused by succinylcholine.