Anabolic androgenic steroids (AAS) are artificial substances, acting through androgen receptors and were primarily developed for the treatment of hypogonadism, tumors, hypercalcemia, hypercalcuria and other chronic diseases. The discovery, in the early 1930s that these substances may have other benefits related to improvement in physique and athletic performance, has encouraged extensive use of these substances by amateur and professional athletes and members of the general public. The range of AAS used can be classified as either endogenous or exogenous. When used for ergogenic or recreational purposes the dosage is more often higher than the recommended dosage, and at supraphysiological levels, AAS can cause a number of serious side effects including liver dysfunction, myocardial infarction and potentially stroke, due to its ability to increase platelet and platelet aggregation. Furthermore, these high dosages may or can affect other physiological systems including the immune system. Hence, this paper reviews the current research on the effects of a number of specific AAS in the immune system.