Does personality affect earnings? If so, are there gender differences in personality that explain part of the gender wage gap? We use survey data collected from over 2,600 Russian employees between 2000 and 2003 to evaluate the impact on earnings of two personality traits: locus of control (Rotter 1966) and challenge-affiliation (Hill et al. 1985). We find that gender differences in personality traits are significant. Men are more likely to exhibit an internal locus of control and need for challenge, while women are more likely to exhibit an external locus of control and need for affiliation. Moreover, there are differences in the effect of personality on earnings by gender - women's earnings are affected by personality, while men's earnings are not. Among participating employees in our study, the "unexplained" portion of the gender wage gap falls by as much as 12% when personality traits are included.