Despite intensive information on possible side effects and complications of performance-enhancing substances in sports, the use of AAS (anabolic androgen steroids) is far common. Particularly in sports like bodybuilding or weight lifting AAS are used for setting up muscle mass and increasing muscle power. We present the case of a 27 year old bodybuilder, who was transferred due to suspected malignant expansion of the upper limb to a department of orthopaedic surgery, not knowing that the patient had injected AAS. At biopsy the tumor was found to be an abscess formation, that had to be treated surgically with curettage. The microbiological analysis detected an infection with Pseudomonas fluorescens and Erwinia species. Erwinia species are associated with plants, Pseudomonas fluorescens is found in feces, sewage and soil. It is obvious, that the infection is caused by an inappropriate injection of AAS or by the contamination of the injected substances.