Assessment of the outcome of obesity operations is exceedingly complex. Currently there is no consensus among bariatric surgeons as to what constitutes successful weight loss. Furthermore, weight loss data must be regularly reevaluated to account for later regaining of lost weight. There is no question that surgically-induced weight loss results in improvement or resolution of obesity-related medical problems in most patients. Yet it is not known whether sustained long-term weight loss will result in extended amelioration of these medical problems. Analysis of outcome is further complicated by difficulties in maintaining consistent long-term follow-up in such a way that the benefits of weight loss can be objectively evaluated. The next decade should provide improvements in a number of these problem areas. The new computer registry of the American Society of Bariatric Surgery has access to thousands of bariatric surgical patients. This registry will hopefully provide for some standardization in analysis and reporting of results of bariatric operations. The registry may eventually be able to provide the type of actuarial analysis of long-term results necessary to assess the true impact of bariatric operations on the morbidity and mortality risks associated with morbid obesity. It is also probable that more sophisticated patient selection methods will improve the likelihood of successful weight loss both by excluding patients who are prone to failure and by identification of patient profiles that are better suited for treatment by one type of operation over another. In the final analysis, there is no question that morbid obesity poses an increased risk to health and longevity. Thus it is only logical that substantial weight loss in this group of patients could be expected to improve both longevity and quality of life, provided that the treatment methods employed are free of serious side-effects. At present, surgery offers the only realistic hope for successful weight loss in the morbidly obese.