Mate choice decisions of animals show significant variability-both among and within individuals. Clearly, such variability can profoundly impact individual fitness, as well as subtly alter sexual selection processes, but we know little about the neural mechanisms underlying such variability. We examined the influence of the neuropeptide arginine vasotocin (AVT) on the strength of attraction of female gray treefrogs (Hyla versicolor) showing positive phonotaxis to the call of a conspecific male. Female treefrogs received intracerebroventricular injections with either saline, AVT (five doses), or the AVT receptor antagonist Manning compound (two doses). By 30 min after injection, AVT significantly increased the speed with which females approached the speaker, at doses of 1, 10 and 50 ng per frog. At the highest dose, the average speed was doubled. The AVT antagonist significantly inhibited phonotaxis at both doses (50 and 100 ng). The effects of AVT on treefrog phonotaxis were shorter lived (disappearing within 60-90 min), compared to Manning compound (effects persisted at least 90 min). These findings support the hypothesis that endogenous AVT is critical to the display of female phonotaxis behavior. AVT may thus contribute to variability in female mate choices by modulating proceptive behaviors.