In a 12-months double-blind study 42 obese patients (5 males, 37 females) were treated either with d-fenfluramine (30 mg daily) or with placebo plus low-calorie diet (1500-1200 kcal daily). Evaluation of treatment efficacy was based on evolution of the initial cohort, weight loss, number of subjects completing treatment, tolerability and events leading to dropout. Patients receiving d-fenfluramine had statistically significant greater weight loss than the placebo group; 30 mg daily proved to be an effective and well tolerated dose of d-fenfluramine with the best long-term activity/acceptability ratio.