In several studies it has been demonstrated that products containing pharmaceutically active ingredients are marketed as dietary supplements. Most of these products contain anabolic steroids. Recently products for weight loss containing active drugs have also appeared on the market. In the present case a healthy male ordered the product ‘Anabolic burner’ via the Internet. The product was received from a German dispatcher and paid by bank transfer to a German bank account. After ingesting one tablet he reported tremor and delivered a urine sample. This urine was found to contain 2 ng/mL of clenbuterol utilizing LC-MS/MS analysis. Additionally the product itself was analyzed with GC-MS for clenbuterol, yielding a content of about 30 µg per tablet. The beta-2 agonist clenbuterol is only legally available on prescription and is classified as prohibited doping substance in sports. The present case for the first time confirms the presence of clenbuterol in a dietary supplement. It again demonstrates the common problem with products on the supplement market, where non-licensed pharmaceuticals and doping substances are easily available. The ingestion of these products containing additions of therapeutic drugs can lead to side effects and/or interactions with conventional medicines. Copyright © 2007 John Wiley & Sons, Ltd.