Twenty-one grossly obese patients were studied before and repeatedly after gastroplasty. Eighteen months after surgery, three groups of patients were identified which had similar preoperative weights but showed significantly different patterns of weight loss. About one third of the patients were considered unsuccessful (less than 20% weight loss). Psychological assessment, using the meta-contrast technique, showed that signs of regressive defense and of immature identity decreased postoperatively. Mild to moderate depressive reactions were found in two thirds of the patients postoperatively and were significantly more frequent among the successful patients. Acute depressive episodes, severe enough to require professional intervention, occurred in four patients, three of whom belonged to the successful group. No correlation could be found between surgical complications or metabolic alterations after gastroplasty and postoperative depression, implying that these factors do not primarily influence the patient's postoperative psychological status. Rather, we suggest that the marked weight loss as such leads to problems of adaptation which in turn may trigger depressive reactions.