SummaryTridestra (Sanofi Winthrop; Orion Pharma, Finland) is a novel hormone replacement therapy designed to aid compliance. It involves the concept of adding a progestagen at the end of every 3 months of oestrogen treatment. This means that withdrawal bleeding occurs at three-monthly intervals. It has been shown in trials comparing 1 and 3-monthly cyclical hormone replacement that menopausal women preferred quarterly withdrawal bleeding to monthly bleeding (Ettingeret al., 1994; Hirvonenet al., 1995). Tridestra is for continuous use with no tablet-free days. Oestra-diol valerate, 2 mg, is taken for 70 days, followed by 20 mg medroxyprogesterone acetate in addition to the oestradiol for 14 days (days 71–84). Each cycle is completed with seven placebo tablets on days 85–91. to aid compliance. Tridestra is licensed for the treatment of climacteric symptoms associated with the menopause and the prevention of postmenopausal osteoporosis in women considered to be at risk of developing fractures.