Treatment of obesity with human chorionic gonadotrophin was shown to be of no better value than saline in a double-blind crossover study of weight reduction in obese subjects. There was also no significant difference in mood, hunger, or missed injections, and no apparent difference in adherence to diet when the two agents were compared. In contrast, a significant difference was found in the ability of subjects to lose weight in the first four weeks of the study in contrast with the second four weeks, no matter which agent was used. Thus, the initiation of a new therapeutic program, even using an inert agent, has a temporary benefit--a manifestation both of placebo effect and the Hawthorne effect.