Women's hours of housework have declined, but does this change represent shifts in the behavior of individuals or differences across cohorts? Using data from the National Longitudinal Surveys, individual and cohort change in housework are examined over a 13-year period. Responsibility for household tasks declined 10% from 1974–75 to 1987–88. For individual women, changes in housework are associated with life course shifts in time availability as well as with changes in gender attitudes and marital status, but are not related to changes in relative earnings. Cohort differences exist in responsibility for housework in the mid-1970s and they persist over the 13-year period. Overall, these findings suggest that aggregate changes in women's household labor reflect both individual change and cohort differences.