The auditory evoked potentials (AEPs) elicited by click stimuli were measured in heterosexual, homosexual, and bisexual males and females having normal hearing sensitivity. Estimates of latency and/or amplitude were extracted for nine peaks having latencies of about 2-240 ms, which are presumed to correspond to populations of neurons located from the auditory nerve through auditory cortex. For five of the 19 measures obtained, the mean latency or amplitude for the 57 homosexual and bisexual females was different from that of the 49 heterosexual females in a manner that implies a masculinization of the auditory systems of the homosexual and bisexual females. A similar masculinization effect was previously observed for the otoacoustic emissions generated by the cochlea. For five other measures, the mean latency or amplitude for the 53 homosexual and bisexual males was different from that of the 50 heterosexual males in a manner that implies a hypermasculinization of the auditory systems of the homosexual and bisexual males. Hypermasculinization has been reported recently for other physical characteristics of homosexual males. One parsimonious interpretation of these findings is that homosexual males and females both were exposed to higher than normal levels of androgens at some point(s) in development. Data are reported only for the female subjects not using oral contraceptives because those drugs can masculinize certain AEP measures.