This paper examines household fertility and female labor supply over the life cycle. The authors investigate ho w maternal time and market inputs, and benefits children yield their parents, vary with their ages and influence female labor supply and c ontraceptive behavior. Their econometric framework combines a female labor-supply model and a contraceptive choice index function and allo ws conceptions not to be perfectly controllable. Using data from the Panel Study of Income Dynamics, they estimate these equations and tes t alternative specifications. The findings suggest that parents canno t perfectly control conceptions and variations in child care costs af fect the spacing of births. Copyright 1988 by The Econometric Society.