The immediate and long-term biologic and behavioral consequences of voluntary ethanol (EtOH) exposure during male adolescence are unknown. In the present study, male golden hamsters voluntarily drank from a 15% EtOH solution in addition to consuming dry laboratory chow and water ad lib from Postnatal Day 25 to Postnatal Day 43. Over this adolescent period, they drank an average of 13 g/kg/day of EtOH, resulting in a mean blood EtOH concentration of ca. 53 mg %. On Postnatal Day 35, a period of enhanced sensitization and activation of the gonadal axis, testosterone levels were twice as high in EtOH animals than in sucrose-yoked controls. However, this difference disappeared by Postnatal Day 53, as EtOH and control animals showed comparable adult levels of plasma testosterone. When tested for aggression several days after the cessation of EtOH exposure, hamsters showed enhanced attack behavior toward smaller intruders placed into their home cage. These results suggest that voluntary EtOH exposure during male adolescence has specific neuroendocrine effects with lasting behavioral consequences.