This chapter examines gender diversity with a focus on the proportion of females in companies in Taiwan. The investigation also examines the effect of the proportion of females on company performance. The research used two Taiwan government databases offering statistics of individual indigenous companies in the manufacturing industries in 1996 and 2001, with a sample size of 8,622 in 1996 and 8,731 in 2001. Results show that the proportion of females in managerial, professional, and administrative jobs is increasing and is positively associated with company performance. By contrast, the proportion of females in operational-level jobs is decreasing, and its association with company performance is inconsistent. This study extends previous gender diversity research in management groups and suggests that women can be invaluable resources for business organizations in Taiwan.