To provide a quantitative comparison of outpatient treatments for obesity, an analysis was made of all such research published between 1966 and 1977. All articles which presented data for five or more healthy outpatients were included. Conclusions were: (1) there has been little improvement in the clinical effectiveness of weight reduction therapy since Stunkard & McLaren-Hume's (1959) review; (2) weight losses produced by different methods, from behavior therapy to anorectic medication, are very much the same; (3) the in-treatment results of diet therapies are the largest of those reviewed and deserve further attention; (4) behavior therapy produces the best maintenance of weight losses, although data from other types of therapy are very scanty; and (5) techniques for motivating clients to adhere to treatment recommendations are needed for improvement in the future. Recommendations for improving the methodology of weight-control research are also presented.