Explanations of the effect of family status on women's work outcomes have focused primarily on individualistic factors, that is, married women's family responsibilities are assumed to interfere with their work performance. Few studies have considered a structural explanation-employers may prefer single and childless women as employees, perhaps because they are assumed to have lower turnover rates than married women with children. This paper tests the structural explanation, using hypotheses derived from labor market segmentation theory. The analysis, based on data from the National Longitudinal Surveys of Mature Women, indicates that the wage advantage of single and childless women is stronger in large firms, where employers are more able to offer promotions and wage increases, and in male-dominated occupations, where employers are more likely to value stable uorkers who will remain with the firm.