"Gaydar" is the ability to distinguish homosexual and heterosexual people using indirect cues. We investigated the accuracy of gaydar and the nature of "gaydar signals" conveying information about sexual orientation. Homosexual people tend to be more sex atypical than heterosexual people in some behaviors, feelings, and interests. We hypothesized that indicators of sex atypicality might function as gaydar signals. In Study 1, raters judged targets' sexual orientation from pictures, brief videos, and sound recordings. Sexual orientation was assessed with high, though imperfect, accuracy. In Study 2, different raters judged targets' sex atypicality from the same stimuli. Ratings of sexual orientation from Study 1 corresponded highly with targets' self-reports of sex atypicality and with observer ratings of sex atypicality from Study 2. Thus, brief samples of sex-atypical behavior may function as effective gaydar signals.