Physicians are reluctant to treat obesity despite the rapid increase in its prevalence in the UK and its associated health problems such as diabetes, coronary heart disease and hypertension. Overweight and obesity are chronic conditions that require long-term treatment. Any therapeutic programme should combine dietary restriction with physical activity and alterations to lifestyle. The use of pharmacological treatment as an adjunct to conventional treatment modalities is justified in certain circumstances. The criteria applied for the prescription of an anti-obesity drug should be comparable to that applied to the treatment of other relapsing disorders. The objective of the Royal College of Physicians' new report, Clinical management of overweight and obese patients with particular reference to the use of drugs, is the provision of such necessary guidance. Based on evidence from clinical trials, the recommendations of the report utilise a 12-week goal (outside a drug trial) of 5% body weight loss from the start of drug treatment. Failure to achieve this goal is an indication for stopping drug therapy. Safety and efficacy demand appropriate use of anti-obesity drugs in a supervised setting with clinicians weighing up likely medical benefit against possible risks.