This study examines whether living with other adults enables married and single mothers in New York City to enter the labor market. Multivariate analyses of data on over 8,000 households revealed that living with coresident adults increased the participation of Puerto Rican, Dominican, and Asian single mothers, and enabled all mothers of young children and all foreign-born mothers to enter the labor market. In a separate analysis of extended households, the proportions of elderly and employed coresident adults increased women 's labor force participation, while the proportion of coresident adults who reported child care/family responsibilities as their reason for not being in the labor force decreased women's paid labor activity. Our findings suggest that coresident adults serve different functions within the household, which in turn influence women's labor force decisions in various ways. In recent years attention has focused on the various ways in which families manage social and economic difficulties. One strategy that has received considerable research attention is household extension, or the incorporation of adults other than the husband and wife into the household. Incorporating other adults may benefit the household in a number of ways. Co-resident adults may contribute to the household's pool of financial resources, thereby potentially increasing the economic well-being of household members. Or they may provide domestic labor, which might enable the wife or female householder to devote more time to paid employment. Angel and Tienda (1982) argued that household extension may be an important adaptive strategy for minority families, in that additional income contributions may compensate for low earnings or sporadic unemployment. In this article we analyze the relationship between household extension and mothers' labor force participation among six racial and ethnic groups in New York City. In so doing, we largely replicate an earlier analysis by Tienda and Glass (1985) using current data from one of the nation's most diverse cities. However, we expand upon the earlier analysis in three ways: by including an indicator of the supply of child care in the household, by examining a broader array of racial/ethnic groups, and by analyzing the role that birthplace plays in influencing women's labor market behavior. DETERMINANTS OF WOMEN'S LABOR FORCE PARTICIPATION Family structure has long been recognized as an important determinant of women's labor force participation. Typically, family characteristics--such as marital status, the presence of young children, and the presence of coresident adults--affect the amount of time women can spend in domestic and market activities. Including other adults in the household may ease the strain of balancing domestic and market responsibilities, especially for single mothers and mothers of young children who may have the least flexibility in devoting time to the labor market. Prior research has shown that women who live in extended households are more likely than women who do not live with coresident adults to be in the labor force, yet this relationship varies by race/ethnicity (Barry Figueroa & Melendez, 1993; Stier, 1991; Stier & Tienda, 1992; Tienda & Glass, 1985). Moreover, women's labor force behavior appears to be influenced by the specific characteristics of coresident adults. For example, as the number of coresident adults increases, married mothers' participation decreases, suggesting greater domestic burdens; by contrast, as the proportion of female coresident adults increases so does single mothers' participation, suggesting that coresident women function as surrogate domestic workers (Tienda & Glass, 1985). Living with coresident employed adults increases labor force participation among young mothers, while living with coresident nonworking adults--presumably a source of child care--depresses paid labor activity (Parish, Hao, & Hogan, 1991). …