According to the family utility function approach, the labor supply functions of married men should differ according to whether their wives also work. In this paper, I explicitly model the switching nature of labor supply while also accounting for the endogeneity of the labor force participation decision of the wife, using an endogenous switching regressions model based on the quadratic family utility function. The model is estimated from a cross section of 1,210 married couples from the Panel Study of Income Dynamics.