The Australian Longitudinal Study on Women's Health was begun in June 1995 in response to initiatives arising from the National Women's Health Policy. Now renamed Women's Health Australia, the study involves six cohorts of women, selected on the basis of age or ethnicity to represent young, middle-aged, and older women (main cohorts), as well as Aboriginal and Tones Strait Islander women and women migrants to Australia (special cohorts). The main themes of the study are time use; health, weight, and exercise; violence against women; life stages and key events; and use of and satisfaction with health care services. Results of pilot studies indicate that it is feasible to use the Health Insurance Commission (Medicare) database as a sampling frame for the three main cohorts and that middle-aged women are more likely than older or younger women to consent to participate. The baseline survey for the main cohorts began in April 1996, with data collection for the special cohorts progressing over 1996-1997 as appropriate consultation with the communities concerned is established. Data from this Australian study should make a valuable contribution to current international efforts to identify the factors that promote and reduce health in women.