[ Abstract IIn the context of house searches in Germany, numerous drugs were confiscated and subjected to chemical analysis, including anabolic agents such as various anabolic-androgenic steroids (stanozolol, testosterone derivatives, trenbolone esters, etc.) and clenbuterol, as well as agents with anti-estrogenic activity (tamoxifen, clomiphene), drugs stimulating virility (sildenafil, tadalafil), and unlabeled plastic bags. Liquid chromatographytandem mass spectrometry, gas chromatography-mass spectrometry with nitrogen-phosphorus specific detection, gel electrophoresis, and immunological tests were employed to test for the effective content of 70 products. In 18 cases (25.7%), the declared ingredients differed from the actual content, in particular concerning anabolic-androgenic steroids. Nandrolone and trenbolone esters, for instance, were frequently substituted or complemented by various testosterone derivatives, and several testosterone depot formulations originally composed of four different esters were found to contain fewer or wrong components. Except for those drugs supposedly originating from so-called underground labs, fake packings were hardly or not distinguishable from original boxes by visual inspection.resulting side effects such as the reduction in vessel-protective HDL cholesterol, early atherosclerosis, prothrombotic effects, liver tumors, and others were observed in numerous case studies with and without lethal consequences (2-11).During the last 10 years, numerous products that supposedly support athletic performance and muscle growth were obtained from different commercial sources (e.g., via Internet order) but also confiscated in house searches. Several of those were identified as counterfeit substances. In the present report, we describe the analysis of 70 products collected from three different individuals under suspicion for dealing with prescription drugs and illegal compounds. As packaging and labels were not differentiable from original counterparts, aliquots of all drugs were subjected to liquid chromatography-tandem mass spectrometry (LC-MS-MS) or gas chromatography-mass spectrometry with nitrogen-phosphorus specific detection (GC-MS-NPD) in order to determine whether these drugs were authentic or fake products. In addition, unlabeled plastic bags were analyzed for their content using MS approaches with and without chemical derivatization.