The purpose of this study is to evaluate the labor supply of married females by using the micro data from the Ministry of Labor's General Survey on Part-time Workers Condition (GSPWC). In particular, we examine the effects of (1) the exemptions for spouse in the husband's income tax, (2) social security contributions (which are means-tested by the wife's income), and (3) allowances for spouse provided by the husband's employer. These three factors are likely to distort the labor supply of married females, although little research has been done to analyze their effects quantitatively. Our empirical results suggest that these factors do distort our understanding of this segment of the work force.