Oral lorcaserin (BELVIQ(®)), a selective serotonin 5-HT2C receptor agonist, is indicated in the US as an adjunct to diet and exercise in the chronic weight management of obese adults, or overweight adults with at least one weight-related comorbidity (e.g. dyslipidaemia, hypertension, type 2 diabetes). This article reviews the pharmacological properties, therapeutic efficacy and tolerability of oral lorcaserin in this patient population. In three large randomized, double-blind, multicentre studies, oral lorcaserin was more effective than placebo in the management of obese and overweight adults with or without type 2 diabetes mellitus. Following 12 months' therapy, significantly higher proportions of lorcaserin than placebo recipients achieved a ≥5 and ≥10 % reduction from baseline in their bodyweight and a significant between-group difference favouring lorcaserin over placebo was observed for the change from baseline in bodyweight. Moreover, among patients who had achieved a ≥5 % reduction in their bodyweight after 12 months' therapy with lorcaserin, a significantly higher proportion who received lorcaserin for a further 12 months than those who switched to placebo maintained ≥5 % weight loss at 24 months. In general, oral lorcaserin was well tolerated in clinical studies, with hypoglycaemia and headache the most frequently reported adverse events in those with or without type 2 diabetes, respectively. According to a pooled analysis, the risk of US-FDA-defined valvulopathy with lorcaserin is generally low and not statistically significantly different from placebo. From these and other data, the FDA has concluded that lorcaserin is unlikely to elevate the risk of valvulopathy.