OBJECTIVETo estimate incidence of endometrial hyperplasia, vaginal bleeding, and menopausal symptoms in women who changed from standard monthly cyclic hormone replacement therapy (HRT) to half-strength estrogen opposed by medroxyprogesterone acetate (MPA) at 6-month intervals.METHODSWe identified 138 women aged 55–75 years who had regularly used HRT at a standard dosage (equivalent to 0.625 mg conjugated estrogen) opposed by cyclic monthly MPA. Each subject's HRT regimen was changed to 0.3 mg/day esterified estrogens (Estratab; Solvay Pharmaceuticals, Marietta, GA) combined with 14-day courses of MPA, 10 mg/day, every 6 months. Endometrial biopsy was repeated after 1 year of the new regimen. Any vaginal bleeding was reported in each patient's daily diary. Menopause symptoms were evaluated using the Greene Menopause Symptom Index.RESULTSAmong 125 women who had biopsy after 1 year of the new regimen, endometrial hyperplasia was found in two (1.6%, 95% confidence interval 0.3%, 6.2%). Of the 125 women, 44% had scheduled bleeding, and 9.4% had unscheduled bleeding. Relative to baseline vasomotor score (range 0–6), an increase of at least 2 U was reported by 20% of subjects at 6 months and by 17% of subjects at 12 months.CONCLUSIONMost women aged at least 55 years can safely switch their HRT regimen from standard dosage HRT to low-dosage estrogen opposed by MPA at 6-month intervals. Moreover, this new HRT regimen causes little vaginal bleeding while maintaining adequate control of menopausal symptoms.