Obesity its complications and its surgical treatment is important for the anaesthesiologist. The pathophysiological and clinical consequences of obesity involve mainly respiratory, cardiovascular and metabolic functions so that the anaesthesia and postoperative care may affect surgical outcome of these patients. The preoperative, the anesthetic management and the postoperative complications of 54 grossly obese patients undergoing weight-reducing abdominal surgery (bilio-pancreatic diversion) have been studied. According to the Authors' experience, careful preoperative evaluation, intraoperative monitoring, postoperative intensive care, are enough to reduce the haemodynamic, respiratory and metabolic complications.