Longitudinal work suggests that sexual orientation can change over time in men and women. These studies, however, may be susceptible to the bias of self-report. The current study therefore examined self-reported sexual orientation in addition to an objective correlate: genital arousal to erotic videos showing males or females. For 52 men (19 heterosexual, 19 bisexual, 14 homosexual) and 67 women (31 heterosexual, 18 bisexual, 18 homosexual), these measures were taken twice, with approximately 1 year between sessions. For self-reported sexual orientation, women reported lower relative stability (weaker correlation) than men over time, even though women did not change more overall (no stronger mean difference) than men between sessions. Bisexual individuals reported lower relative stability and more mean change than heterosexual and homosexual individuals. For genital arousal, across all groups, response patterns were correlated over time to a similar extent and showed little difference between sessions. Moreover, change in self-reported sexual orientation did not correspond with the change in genital arousal, regardless of sex. Perhaps self-reports overestimate changes in sexual orientation, since these changes were not reflected in physiological sexual response.