Phenmetrazine hydrochloride was used, alternating with a placebo, in a weight reduction program that included diet therapy, close doctor-patient cooperation, follow-up visits, exercise, and instruction in posture. The usual dosage was one 25-mg. tablet by mouth before the noon and evening meal; the maximum dosage was three tablets thrice daily to a total of 225 mg. Effects of suggestion were eliminated by a double-blind method of administering drug and placebo; odd-numbered patients were started on placebo, even-numbered on drug therapy. Each drug (or placebo) period lasted four weeks. At the end of each period, each patient was automatically shifted to the drug or placebo group, depending upon what he had received during the previous period. The patients were studied from a minimum of 8 weeks to a miximum of 35 weeks. Fifty-seven (61.2%) of the 93 patients treated lost an average of 0.86 kg. (1.9 lb.) per week while receiving phenmetrazine as compared with 0.25 kg. (0.54 lb.) average weekly weight loss while receiving the placebo. The importance of the double-blind technique was illustrated by the occurrence of anorexia, nausea, xerostomia, insomnia, and nervousness in 15 patients during placebo periods. Side-effects during periods of active medication were easily controlled.