The aim of this study is to investigate the effects in vitro induced by androgenic anabolic steroids (AAS) (testosterone, nandrolone, androstenedione, norandrostenedione, and norandrostenediol) used illicitly in sport competitions, on the proliferation ability, apoptosis and the intracellular calcium concentration ([Ca2+]i) in human umbilical vein endothelial cells (HUVECs), selected as a prototype of a biological target system whose structure and function can be affected by steroids. For this purpose, we evaluated the proliferation inhibition by cytotoxic assay expressed as the concentration of drug inducing a 50% decrease in growth (IC50). The IC50 was reached for testosterone at 100 microM, androstenedione at 375 microM, nandrolone at 9 microM, norandrostenedione at 500 microM. The IC50 value for norandrostenediol was not reached until a concentration of 6000 microM. The apoptotic effect was evaluated by flow cytometry at IC50 for each drug. We observed that testosterone induced 31% of apoptotic cells, norandrostenedione 25%, androstenedione 15% and nandrolone 18%. We have analyzed the effects of these drugs on [Ca2+]i both in the immediate and long-term continuous presence of each compound. Our data show a statistically significant increase of [Ca2+]i in the acute condition and in long-term treated cultures, suggesting that androgen steroids modulate intracellular levels of calcium independent of incubation time or compound identity. As a whole, this study demonstrates that AAS might alter endothelial homeostasis, predisposing to the early endothelial cell activation that is responsible for vascular complications observed frequently in AAS users.