A number of severe rhabdomyolysis with acute renal failure have been reported following spine surgery in knee chest position. CPK were measured postoperatively in 93 patients (A group), comparatively with two groups in which respectively neurosurgery without any muscle stretching (B group) and abdominal surgery with aid of retractors (C group) were performed. CPK were significantly and similarly increased in A and C groups only. This postoperative increase of CPK appears to be related more to the muscle stretching than to the posture itself. Intraoperative low blood pressure and an operating time longer than 4 hrs contribute probably to rhabdomyolysis. No renal failure was observed in our series. Low limb vascular insufficiency is the main contra-indication of knee chest position. Postoperative diuresis surveillance is mandatory in all cases, CPK analysis is not.