Objective: To determine health care resource use by new postmenopausal users of hormone replacement therapy. Method: We used the Saskatchewan Health administrative databases, which include a health insurance registration file, a cancer registry, and files with data on outpatient prescription drugs, hospital services, and physician services. Our population included postmenopausal women aged 55 years and over with intact uteri taking hormone replacement therapy for long-term prevention benefits, and an equal number of postmenopausal women with intact uteri with no medical contraindications to hormone replacement therapy but who did not use the therapy during the study period. Results: The population in our analysis included 2632 women with new episodes of hormone replacement therapy, all with at least 3 years of follow-up. Only 42% of new hormone replacement therapy users continuously took HRT during the first year after initiation of their first new episode; a third of these were full-year users in the second year. New users of hormone replacement therapy over a 6-year follow-up period had significantly higher rates of medical care contact for diagnoses of menopausal disorders in the first year of HRT compared with subsequent years. We also found slightly elevated numbers of visits to primary care physicians and obstetrician-gynecologists and slightly increased use of endometrial biopsies and dilation and curettage procedures in the first year of hormone replacement therapy, compared with subsequent years. Conclusion: New users of hormone replacement therapy had higher rates of medical care for menopausal disorders in their first year of therapy compared with rates in subsequent years. After discontinuing hormone replacement therapy, utilization of medical care decreased dramatically. (Am J Obstet Gynecol 2001;185:318–26.)