This paper extends a standard intertemporal labor supply model to account for progressive taxation as well as the joint determination of hourly wages and hours worked. We show that these two factors can have implications for both estimating labor supply elasticities as well as for using these elasticities in tax analysis. Failure to account for wage-hours ties and progressive taxation may cause the hours response to marginal tax rate changes to be understated by 5 to 30 percent for men. (Contains 3 tables, 2 figures and 28 footnotes.)