We investigated the effect of an endoscopically placed gastric balloon, the Garren-Edwards gastric bubble (GEGB), on weight loss in obese patients. Fifty-nine obese patients were entered into a prospective double-blind study and randomized into two groups. In one group (34 patients) the GEGB was inserted, and in the other group (25 patients) a sham insertion was done. All patients participated in a standard weight loss program consisting of dietary therapy, behavior modification, and physical exercise. The bubble was removed endoscopically after 3 months from both groups. Patients were followed for an additional 9 months after bubble removal and weight loss was monitored. Weight loss was the same in both groups at 3 months (18.7 lb vs. 17.2 lb). This was true whether determined by change in pounds, percentage of body weight, or body mass index. We concluded that the GEGB was of no added benefit as compared with sham insertion, when combined with a standard weight loss program. Because of the lack of proven efficacy and the relatively high cost, we recommend that such devices be restricted to controlled studies until significant benefits are proven.