Antiobesity treatment is recommended for selected patients in whom lifestyle modification is unsuccessful. Two antiobesity drugs are currently licensed for long-term use. Orlistat, a gastrointestinal lipase inhibitor, reduces weight by around 3 kg on average and decreases progression to diabetes in high-risk patients; adverse gastrointestinal effects are common. Sibutramine, a monoamine-reuptake inhibitor, results in mean weight losses of 4-5 kg, but is associated with increases in blood pressure and pulse rate. Rimonabant, the first of the endocannabinoid receptor antagonists, reduces weight by 4-5 kg on average and improves waist circumference and concentrations of HDL cholesterol and triglyceride; however, an increased incidence of mood-related disorders has been reported. To date, all antiobesity drug trials have been limited by their high attrition rates and lack of long-term morbidity and mortality data. Other promising antiobesity drugs, including those acting within the central melanocortin pathway, are in development, but are years away from clinical use. In light of the lack of successful weight-loss treatments and the public-health implications of the obesity pandemic, the development of safe and effective drugs should be a priority. However, as new drugs are developed we suggest that the assessment processes should include both surrogate endpoints (ie, weight loss) and clinical outcomes (ie, major obesity-related morbidity and mortality). Only then can patients and their physicians be confident that the putative benefits of such drugs outweigh their risks and costs.