This paper applies production theory to define a new set of inputs for U.S. households over the post-World War II period and uses newly constructed data on some of these inputs to fit a complete household-demand system, including inputs of women's and men's housework, and seven other input groups. The econometric results yield plausible price and income elasticities. Women's and men's housework are shown to be complements, rather than substitutes, but the other seven input categories are substitutes for women's housework. Since the price of all inputs, except for men's housework, has fallen significantly relative to the price of women's time over the post-war period, substitution away from women's household work is a major factor in its decline over the study period. Much of this decline, however, occurred from 1948 to 1980. Although the number of children under age 5 per household grew from 1948 to 1960 by 25 percentage points, family size declined from 1960 to 1985 by 27 percentage points and contributed to the post-60s decline in the demand for women's housework. The parameters of the demand system are also used to make some standard of living comparisons for the post-war period.