Objective: To assess the efficacy of cyclic postmenopausal hormone replacement in treating urinary incontinence in hypoestrogenic women. Methods: Eighty-three hypoestrogenic women complaining of urinary incontinence were included. All patients were community-dwelling, age 45 years or older, with involuntary loss of urine occurring at least once a week and urodynamic evidence of genuine stress incontinence and/or detrusor instability. Evaluation consisted of a comprehensive clinical and urodynamic research protocol. The hypoestrogenic entry criterion was a plasma estradiol level of 30 pg/mL or less. Parabasal cells on vaginal smears were also monitored. The primary outcome was the number of incontinent episodes per week, as documented on a standardized urinary diary. Secondary outcomes were the quantity of fluid loss, voluntary diurnal and nocturnal micturition frequency, generic and condition-specific health-related quality of life measurements, and patient satisfaction. A randomized, placebo-controlled, double-blind design was used. Subjects in the treatment group were given conjugated equine estrogens (0.625 mg) and medroxyprogesterone (10 mg) cyclically for 3 months. Controls received placebo tablets. Results: (All results are presented as mean ± standard deviation.) Subjects were 67 ± 9 years old. The menopause duration was 18 ± 11 years. The duration of incontinence was 9 ± 9 years. Estradiol level at baseline was 9 ± 9 pg/mL, and the parabasal cell count was 42 ± 44%. The number of incontinent episodes at baseline was 13 ± 10 for the treatment group and 16 ± 4 for controls. No significant changes occurred in the number of incontinent episodes after treatment: 10 ± 10 for the treatment group, and 13 ± 14 for the controls (P = .7). Also, fluid loss was not changed: 176 ± 106 g for the treatment group and 64 ± 88 g for the control group at baseline, and 101 ± 150 and 51 ± 69 g after treatment, respectively (P = .7). There were no significant differences for either diurnal or nocturnal voluntary micturition, quality of life measures, or patient's perception of improvement. Conclusion: Three-month cyclic hormone replacement therapy did not affect either clinical or quality of life variables of incontinent, hypoestrogenic women. Long-term effects are unlikely to be substantially different. The use of estrogen supplementation as preventive or adjuvant therapy was not evaluated in this study.