In the past decades fitness centers and mass sport events such as public fun biking or city marathons have become essential elements of recreational and mass sport. When looking at fitness centers and other options in the recreational area, motivations of those participating in physical activities are quite different. Those practicing endurance sport wish to improve their general fitness, to reduce their weight or they do it just for fun. Customers of fitness centers normally aspire to improved strength and rapid muscle increase. In this context, doping and drug abuse in recreational and mass sports represent a problem which should not be underestimated. Prohibited substances are taken with a view to overcome individual limits of performance. Numerous of these substances are on the list of prohibited substances and methods published by the World Anti-Doping Agency (WADA). Depending on the type of the practiced activity prohibited drugs are taken primarily to reduce pain or to achieve rapid muscle growth. To reduce pain, non-prescription, over-the-counter (OTC) medicines are often taken over a prolonged period of time since they are easy to get; in contrast to this, doping agents or substances to achieve rapid muscle increase are more difficult to obtain. Internet-based distribution of substances encourages misuse on the one hand and - like products purchased on the black market - implies a considerable risk to get a product which does not comply with certified quality standards. Potential side effects are underrated completely. Doping and drug abuse impair a healthy organism; physical and psychotropic side effects and in case of prolonged misuse - long-term damages are the logical consequence. Thirty years of experience show that the liver and the kidneys are affected in particular. In the majority of cases, drug abuse in marathon running (normally analgesics) is not identified. We do not criticize the nonrecurrent consumption of analgesics in case of unspecific pains. Repeated consumption, however, should be avoided and, alternatively, a doctor should try to find out the reason for the pains. In the areas of recreational and mass sport this is often not done since people feel they do already know the reason (injuries or overtraining). Consequently, there is a gradual development from repeated consumption to definite misuse. In contrast to this, the consumption of substances with a view to increase performance (to develop strength and to achieve rapid muscle increase) must be strictly classified as doping and misuse. In these cases, it is necessary to identify the misuse in order to take adequate measures. The consumption of anabolic steroids and complementary substances in the area of fitness sports results in distinct changes of the body shape and visible changes of the skin structure. For a doctor, these changes can be an indication of misuse, thus giving him an opportunity to inform his patient about potential health risks.