This article examines the influence of family structure on children's short-term psychosocial behavioral outcomes, including emotional disorder, conduct disorder, and prosocial behavior. The analysis uses five waves of data (1994-2003) from Canada's National Longitudinal Survey of Children and Youth to model how living in a cohabitational household (two biological parents) and how experiencing cohabitation dissolution influence children's behaviors, comparing these effects to outcomes observed in children from married biological-parent households. The findings indicate that growing up in a married biological-parent household does not offer a clear advantage. Most differences in behavioral problems across family structure associate with household demographics, low-income status, family dysfunction, and parental nurturance. As such, this study contributes two important findings. First, the results do not support the hypothesis that nonmarital cohabitation represents an undesirable child-rearing environment. Second, cohabitation dissolution has a nonsignificant effect on children's behaviors, which is surprising considering that divorce has a well-established harmful effect. (Contains 1 figure and 4 tables.)