Thirty-one severely obese adults participated in behavioral weight control groups. In three groups utilizing powerful monetary contracts, subjects deposited substantial sums of money which were returned contingent on either attendance, calorie restriction, or weight loss. Subjects in a fourth no-contract control condition made no monetary deposits. Weight and calorie contract groups lost an average of nearly 20 lb in 10 weeks. They did not differ from each other, but both produced significantly more weight loss than the attendance contract group. High dropout rates in the no-contract condition precluded statistical evaluation of this group. Results are discussed in terms of the potential clinical value of contracting procedures.