The endocannabinoid system (ECS) is a complex physiologic system that affects metabolic pathways. A dysregulated ECS has been demonstrated in animal models of obesity and the expression of the cannabinoid type 1 (CB(1)) receptor in both brain and peripheral tissues suggests that selective antagonism at this receptor could target multiple tissues involved in metabolic homeostasis. In clinical trials with obese patients, treatment with the CB(1) receptor antagonist rimonabant was associated with clinically meaningful weight loss, as well as improved serum lipids and glycemic control. The biological basis for the metabolic effects of rimonabant (SR141716) appears to involve the modulation of metabolism through antagonism at a single receptor with several target organs.