Dexfenfluramine is one of the most widely prescribed appetite suppressant drugs in Switzerland because of its enhancing effect on certain weight-reducing diets. Nevertheless, the effects of acute intoxication are not well documented. We recently observed a young adolescent girl who ingested large quantities of the drug to achieve a rapid weight loss. She presented with tachycardia, high blood pressure, mydriasis, fever and behavioral disorders. All signs and symptoms cleared after 48 hours. The clinical picture is akin to amphetamine intoxication, in view of the similarity of the two drugs' metabolites.