Centrally acting appetite suppressant drugs used in the treatment of obesity fall into 2 broad pharmacological categories; those which act via brain catecholamine pathways and those which act via serotonin pathways. Of the former group, amphetamine and phenmetrazine are no longer recommended because of their stimulant properties and addictive potential. The remaining drugs in this class include amfepramone (diethylpropion), phentermine, mazindol and phenylpropanolamine. All have been shown to reduce appetite and lower food intake, thereby helping obese patients more easily keep to a low-calorie diet and lose weight. They all have some sympathomimetic and stimulant properties. Anorectic drugs which promote serotonin neurotransmission have no such stimulant or sympathomimetic properties. They are fenfluramine, together with its recently introduced dextrorotatory stereoisomer dexfenfluramine, and fluoxetine. They reduce appetite and food intake and are effective in the treatment of obesity. Anorectic drugs should be reserved for those who are clinically at risk from being overweight, and then only as part of a comprehensive weight-reducing programme including regular dietary counselling. Although current licensing regulations only allow their use over a relatively short period (12 to 16 weeks), clinical trials have shown them to be effective over longer periods, particularly in preventing weight regain. Of the compounds currently indicated for use in obesity, dexfenfluramine appears to have the most suitable pharmacological profile, although it should not be given to patients with a history of depression. When used appropriately, appetite suppressants can be of real therapeutic benefit, and pose little risk.