Anabolic androgenic steroid (AAS) is the familiar name for synthetic derivatives of the male sex hormone, testosterone. A large number of young adults abuse AAS to enhance performance and physical appearance. The aim of this study was to evaluate the effects of AAS abuse on the gingival tissues in a group of bodybuilders and weight lifters. The test group was composed of 24 athletes aged between 17 and 29 years who had been using AAS for >1 year. All subjects were clinically examined for plaque levels (plaque index), gingival inflammation (gingival index), and gingival enlargement. The results were compared to a control group of 20 bodybuilders who had never used AAS drugs and who matched for age, educational level, and oral habits according to the data obtained from the test group. Although there were no statistical differences between the plaque index (P>0.05) and gingival index (P>0.05) scores of the study group and the control group, the AAS abusers had statistically higher scores of gingival thickness, extent of gingival encroachment, and total gingival enlargement scores (P<0.001 each) compared to non-users. The results of this study have revealed that the prolonged use of AAS is closely associated with significant levels of gingival enlargement. Because recreational abuse and abuse in non-competitive sports seem to increase despite legislation, dentists and periodontists should be familiar with the adverse effects of these synthetic derivatives of testosterone on the gingival tissues.