Anabolic steroids have been employed extensively in equine practice over the past 25 years. Their usefulness is largely dependent on subjective opinions, as only minimal studies have been carried out in horses. Therefore, their use will vary markedly between practitioners depending on their personal experiences and pressures by trainers to use them. They form part of rational therapy in a variety of conditions. In addition to use for increasing muscle mass, they are used to a varying extent in the raising of yearlings and in the training and racing of horses with the view of improving performance. However, in almost all countries, the latter use is largely curtailed, and the presence of these substances in postrace urine samples constitutes use of an illegal substance. To detect the use of anabolic steroids, including testosterone, sensitive ELISA tests for screening and GC/MS for confirmation have been developed. These compounds can be used safely. Risks can be encountered if too high doses are used, as horses may become difficult to manage due to increased aggressiveness and other stallion-like behavior. Reproductive efficiency in both stallions and mares may be temporarily impaired, but this is quite rapidly reversible following cessation of treatment.