Male leopard geckos that hatch from eggs incubated at a female-biased temperature (T f ) behave differently when compared with males hatching at a temperature which produces a male-biased sex ratio (T m ). We investigated the effect of incubation temperature and androgen implantation on aspects of the dopaminergic system of T f and T m males. Our data suggest that more dopamine (DA) is stored in the nucleus accumbens of naive T f males compared with naı ¨ve T m males when they encounter a receptive female conspecific across a barrier. No difference was measured in the preoptic area and the ventral tegmental area (VTA). This difference in intracellular DA levels in a motivationrelated brain nucleus might be correlated with differen-ces in sociosexual behavior observed between the two morphs. There were no differences in tyrosine hydroxylase (TH) expressing cell numbers in the VTA of cholesterol (CH)-implanted naive castrated T f and T m males. Only T f males implanted with testosterone had significantly higher TH immunopositive cell numbers in the VTA compared with CH-and dihydrotestosteroneimplanted T f males. These data indicate that both the embryonic environment as well as the circulating hormonal milieu can modulate neurochemistry, which might in turn be a basis for individual variation in behavior.