The current chapter reviews theory and findings with regard to relationships between gender and organizational citizenship behavior (OCB). Based on self-report OCB studies, female employees tend to report that they perform more communal OCB (e.g., altruism) than do male employees, whereas male employees tend to report that they perform more agentic OCB (e.g., sportsmanship) than do female employees. However, supervisors do not appear to rate male and female employees differently on OCB performance. Our review also suggests that even with the same amount of OCB performance, female employees tend to be disadvantaged with regard to career-related outcomes (e.g., promotion) relative to male employees. For future research, we encourage researchers to distinguish between actual and perceived OCB performance and examine associated gender differences. Measurement invariance of OCB across gender, different career success outcomes between males and females, and the effects of gender egalitarianism in cultures also need further investigation.