We use time-diary data from the 2003 and 2004 American Time Use Surveys and the 2000 United Kingdom Time Use Study to estimate the effect of family structure on the time mothers and fathers spend on primary and passive child care and on market work, using a system of correlated Tobit equations and family structure equations. Estimates from these models indicate that single parents in both countries spend more time in child care than married or cohabiting parents. There are differences, however, in market work with single parents in the U.S. working more than other parents and single parents in the U.K. working less.