Background: While there is emerging evidence that sedentary behavior is negatively associated with health risk, research on the correlates of sitting time in adults is scarce. Methods: Self-report data from 7724 women born between 1973-1978 and 8198 women born between 1946-1951 were collected as part of the Australian Longitudinal Study on Women's Health. Linear regression models were computed to examine whether demographic, family and caring duties, time use, health, and health behavior variables were associated with weekday sitting time. Results: Mean sitting time (SD) was 6.60 (3.32) hours/day for the 1973-1978 cohort and 5.70 (3.04) hours/day for the 1946-1951 cohort. Indicators of socioeconomic advantage, such as full-time work and skilled occupations in both cohorts and university education in the mid-age cohort, were associated with high sitting time. A cluster of 'healthy behaviors' was associated with lower sitting time in the mid-aged women (moderate/high physical activity levels, nonsmoking, nondrinking). For both cohorts, sitting time was highest in women in full-time work, in skilled occupations, and in those who spent the most time in passive leisure. Conclusions: The results suggest that, in young and mid-aged women, interventions for reducing sitting time should focus on both occupational and leisure-time sitting.