The aim of this paper is to simulate the effects of the Spanish 1999 tax reform on married women's labour suplly and welfare in a partial equilibrium context. We estimate bay maximun likelihood two models of labour suplí wich take into account the characteristics of the budget constraint. The results of the simulation exercise show that the new tax system will, in general, imply a fall in the participation of married women, as well as an increase in the net income and welfare of their households. These welfare increases are more important the higher the potential income of the household, and the greater the number of children.

Key words: labour supply, direct taxation, simulation.
JEL classification: J22.