STUDY OBJECTIVE To prospectively evaluate the clinical effectiveness and safety of ultrasound-guided percutaneous microwave ablation for symptomatic subserosal uterine myomas. DESIGN Prospective observational study (Canadian Task Force classification II-1). SETTING A teaching hospital (Department of Interventional Ultrasound, General Hospital of Chinese PLA, Beijing, China). PATIENTS Sixty-nine patients with symptomatic subserosal uterine myomas treated with ultrasound-guided percutaneous microwave ablation. INTERVENTIONS All 69 patients underwent ultrasound-guided percutaneous microwave ablation. The number of patients lost to follow-up at was 21 at 3 months, 34 at 6 months, and 35 at 12 months. MEASUREMENTS AND MAIN RESULTS The efficacy of treatment was evaluated based the mean myoma volume shrinkage rate and changes in Uterine Fibroid Symptom and Quality of Life Questionnaire scores at 3, 6, and 12 months after therapy. Treatment safety was evaluated based on the Society of Interventional Radiology practice guidelines. The mean patient age was 40.3 ± 4.9 years (range, 26-49 years). The mean myoma volume was 221.74 ± 153.18 cm3 before ablation, decreasing to 87.24 ± 45.93 cm3 at 3 months after ablation (p < .001), 46.68 ± 24.7 cm3 at 6 months after ablation (p < .001), and 38.05 ± 24.93 cm3 at 12 months after ablation (p
