The role of serotonin (5-HT) in appetite control is well recognised. 5-HT drugs reduce food intake in rodents in a manner consistent with an enhancement of satiety. In humans, they have been shown to reduce caloric intake, an effect associated with reduced hunger and increased satiety. These effects appear to be mediated, at least in part, by the 5-HT(2C) receptor subtype. 5-HT-acting drugs such as fenfluramine, d-fenfluramine, and sibutramine have provided effective anti-obesity treatments in the past. However, more selective agents are needed that produce the same changes in eating behaviour and induce weight loss without unacceptable side effects. Lorcaserin, a selective 5-HT(2C) receptor agonist, is a novel anti-obesity agent that reduces both energy intake and body weight. The effects of lorcaserin on eating behaviour remain to be characterised as does its behavioural specificity.