Analysis of annual Current Population Survey data from 1947 to 1985 reveals that increased female labor force participation equalizes the income distribution of male-headed income-receiving units and husband-wife families. For male-headed units, increased female labor force participation reduces the income share of the top quintile, suggesting that assimilating females decrease the earnings of men in high-wage occupations. For husband-wife families prior to 1970, equalizing impacts stem from relatively high participation rates of women married to low-earning men. After 1970, however, increased participation came mainly from women with above-average earnings growth who were married to high-earning men. Hence, continued increased female labor force participation may increase inequality for dual-earning husband-wife families.