This study investigated the influence of gonadal hormones and sexual experience on behavior, especially vocalizations, of male bank voles ( (Schreber, 1780)) during same-sex encounters in a neutral arena. Interactions within pairs of castrated males, castrated but testosterone-treated males, and sham-operated intact males were studied in the first experiment and within pairs of sexually experienced males and sexually inexperienced males in the second experiment. Castration reduced the number of ultrasonic vocalizations emitted and androgen treatment restored it to levels seen in intact males. Ultrasounds were emitted more frequently during amicable encounters than during aggressive ones, but ultrasonic calling was reduced during interactions between sexually experienced males, possibly because of the high level of aggression seen in such encounters. In contrast, audible sounds were associated with aggressive behavior and were positively affected by social experience, but they were not testosterone dependent. Neither testosterone nor sexual experience appeared to have any effect on the spectral and temporal characteristics of either audible or ultrasonic calls. The results indicate that emission of ultrasounds during same-sex encounters of male bank voles is regulated by hormonal and social factors and seems to be correlated with type of behavior shown.