During the last half of the 20th century, married women with children moved into the labor force in large numbers. This change, which occurred throughout the industrialized world, dramatically altered work, family, and gender roles. Working parents today juggle demanding jobs and busy family lives and find it increasingly difficult to balance these activities. Work-family conflict has become a pressing social issue. This article examines four areas of social science research on work and family, including: work-family conflict, spillover, and multiple roles; work-family policies in organizations; effects of work on family life; and cross–national research on work and family. Although much is known about all of these topics, more research is needed to address the work-family challenges of the 21st century.