One hundred and twenty-nine obese patients, whose obesity was not caused primarily by organic-factors, were followed for 6 mo. in a weight reduction study which particularly controlled for the effects of group discussion sessions, and of a dextroamphetamine sulfate - prochlorperazine sustained-release capsule. Patients in the group discussion sessions were more successful in losing weight than patients who received medical care equivalent to that received from a family physician. Patients receiving the drug clearly performed better in the 1st mo. of the program. However, the wide individual variability of performance over the 6 mo. within the drug regimen (and within all regimens), and the precipitous decline in performance of those on the drug during the latter portion of the 6 mo., are among factors which qualify the confidence one might have in the effectiveness of this and similar drugs. Characteristics of the successful, as compared with the non-successful, dieter were extracted from psychological instruments, questionnaires, and the noted observations of the investigators. Salient characteristics of the successful dieter were: A reasonable understanding of the source of obesity (overeating played a primary role in all patients considered here), self-motivativation to lose weight, and sufficient psychological resiliency to emotionally adapt to a sustained reduction in eating. Such resiliency is not equivalent to lack of psychopathology. Little psychiatric screening was done, but none of the patients met any psychiatric emergencies as a result of dieting. General ideas about the necessary elements of an effective weight reduction program are offered, along with discussion of the reasons why even relatively intensive programs are successful with only a small proportion of patients.