The results of 105 studies of self-control behavioral treatments of obesity were analyzed to examine the effects of treatment characteristics on outcome. The mean posttreatment weight loss of the 6,121 subjects was 5.64 kg, and the mean follow-up loss of 5,453 subjects was 5.38 kg. Posttreatment losses were positively associated with treatment duration, hours of treatment contact, therapist experience, following a rigorous diet, practicing physical exercise during treatment sessions, involvingthe dieter's family, and providing anorectic drugs. Follow-up losses were associated in the same way with the first five of these factors, but maintenance was adversely affected by anorectic drugs. The results highlight the role of treatment duration and contact hours, variables which have been neglected by experimental studies. It was argued that taking these factors into account could help to reconcile inconsistent research findings.