OBJECTIVE: To identify predictive factors that will ensure successful menorrhagia treatment using hot fluid balloon endometrial ablation. METHODS: This is a prospective study on patients referred for menorrhagia and treated with hot fluid thermal balloon ablation. Potential prognostic factors for assessing the success of treatment were recorded. Success was defined as patient satisfaction and no subsequent hysterectomy at 2-year follow-up. RESULTS: A total of 130 women were included in the final analysis. The cumulative rate of patients undergoing a hysterectomy after 2 years was 12%. After 2 years, 81% of the remaining patients were satisfied with the results of the treatment. Predictive factors for adverse outcome were a retroverted uterus (hazard rate ratio 3.3, 95% confidence interval [CI] 1.2, 8.6), pretreatment endometrial thickness of at least 4 mm (hazard rate ratio 3.6, 95% CI 1.3, 11), and the duration of menstruation (hazard rate ratio 1.2, 95% CI 1.0, 1.3, per day in excess of 9 days). The risk of an adverse outcome declined steadily with increasing age (hazard rate ratio 0.86, 95% CI 0.77, 0.96 per year over 42 years of age). Uterine depth and dysmenorrhea were not predictive factors, which significantly affected outcome. CONCLUSION: Young age, retroverted uterus, endometrial thickness of at least 4 mm, and prolonged duration of menstruation were associated with an increased risk of treatment failure. Uterine depth and dysmenorrhea had limited impact on the effectiveness of balloon ablation.