Because operations for constriction of the stomach are large and complicated abdominal cavity operations, generation of several complications is a possibility. As compared to the patients in normal weight, the overweight patients have complications more often. The probability of early (30 days as from operation) complications is on average 2-3%. 97% of bariatric operations go without complications. If complications develop, patient must stay in hospital for longer than originally planned. Necessity may arise for repeat operations, blood transfusion, intensive and antibacterial treatment. Later complications may manifest themselves during the whole remaining life span.