We conducted a double-blind test to examine whether or not the addition of mazindol, an appetite suppressor, to combined diet therapy [low-calorie diet + Optifast: 4600-3928kj(1100-940 kcal)/day] enhances the weight-reduction effect and reduces dropout from treatment in women with severe obesity. All of the patients were enrolled in the combined diet therapy and exercise [1255kj(300 kcal/day)] for 7 months. At the end of the first month, the patients were given, at random, three tablets of either 0.5 mg mazindol (18 women) or placebo (18 women) per day, in three doses for three months, in addition to the diet and exercise therapies. At 7 months, the key for the double-blind test was opened by the controller. Four of the 18 patients in the placebo group dropped out of the programme at 2 months after drug treatment, because they could not endure the intense hunger. Therefore, data for these 4 patients were excluded from evaluation. However, none of the patients treated with mazindol + combined diet therapy dropped out. The body weight and body-fat ratio showed marked reduction (p < 0.01 vs. premedication weight). The percent weight loss and percent reduction in body-fat ratio in the mazindol group was significantly (p < 0.01) greater than those found in the placebo group, which also showed a significant decrease in body weight and body-fat ratio (p < 0.01 vs. pre-medication weight) during the same period.(ABSTRACT TRUNCATED AT 250 WORDS)