Abstract From the population of 89 adult sexually inexperienced Wistar male rats 20 animals that initiated copulatory behavior with females exhibiting low intensity of precopulatory behavior (presenting females) were preselected. Prior to castration all 20 males had the same sexual experience: three ejaculatory series in four weekly sessions with females exhibiting high intensity of precopulatory behavior (darting females). Following castration, the decline of copulatory behavior was much slower for the nine males tested with darting females as compared to the 11 males tested with presenting females. Male precopulatory behaviors (anogenital sniffing, touching flanks, etc) outlasted the loss of copulatory behavior and seem to be less dependent on both external and internal determinants. It is concluded that intensive external sexual stimuli can function to compensate, and therefore mask, the subnormal operation of androgen-dependent mechanisms in initiating the copulatory behavior.