Several personality traits, including aggressiveness and sensation seeking, have been hypothesized to be influenced by prenatal androgen exposure, though evidence for this proposition is limited. We investigated whether individual differences in aggressiveness, sensation seeking, and several prosocial personality traits can be predicted from differences in the 2D:4D digit ratio, a putative marker of prenatal androgen activity. A total of 164 undergraduates (87 men, 77 women) completed self-report measures of physical and verbal aggression, as well as a standardized measure of sensation seeking, and five scales to assess empathy, nurturance, expressivity/femininity, instrumentality/masculinity, and assertiveness. Two sex-dimorphic tests of spatial ability also were included. Men had a lower 2D:4D ratio than women, confirming the typical sex difference in digit proportions. Significant sex differences were observed on 10 of the 11 personality scales purported to show sex differences and on both tests of spatial ability. The 2D:4D ratio was a significant predictor of scores on three of the four aggression subscales, total aggression, thrill and adventure seeking, and total sensation-seeking, in the sample as a whole and in women. In men, correlations with 2D:4D were significant only for total sensation-seeking and verbal aggression. In both sexes, lower 2D:4D ratios were associated with increased aggressiveness and sensation seeking. For the spatial tests, there was no evidence of any association with 2D:4D in either men or women. The 2D:4D digit ratio may be a valid, though weak, predictor of selective sex-dependent traits that are sensitive to testosterone.