Study Objective: To assess the long-term efficacy and rate of reintervention after ultrasound-guided radiofrequency thermal ablation (RFA) for uterine myomas. Design: A retrospective follow-up, cohort study (Canadian Task Force classification II-2). Setting: University hospitals and private clinics. Patients: Between November 1, 2007, and February 26, 2010, 66 consecutive women underwent ultrasound-guided RFA. Interventions: Patients underwent abdominal or vaginal ultrasound-guided RFA and were contacted for a long-term followup to complete the Uterine Fibroid Symptom and Quality of Life Score (UFS-QOL) questionnaire and optional ultrasound and examination. Measurements and Main Results: Sixty-six consecutive patients (mean age 45 7 years) with type 2 to 5 symptomatic myomas per the International Federation of Gynecology and Obstetrics (median size = 122.5 cm(3) [range, 24-6751) were included. Forty of 62 patients recruited for follow-up underwent no/minor hysteroscopic reinterventions; 35 patients from this group completed the UFS-QOL questionnaire and showed sustained and improved symptom severity scores (100-point scale) from baseline (57.2 +/- 16.6) to long-term follow-up (23.8 +/- 20.8, p <.001). Twenty-two patients (35%) had major reinterventions (15 hysterectomies and 7 myomectomies). Six of the 22 patients underwent major reinterventions for reasons other than myoma-related complaints. The estimated major reintervention rate because of myoma-related symptoms determined by the Kaplan-Meier method was 13.5%(95% confidence interval [CI], 7%-25%) after 2 years and 29.1% (95% CI, 19%-43%) after 5 years. Women >= 45 years of age had a major reintervention rate of 12% (95% CI, 5%-26%) after 2 years and 19% (95% CI, 10%-35%) after 5 years, and women <45 years had a major reintervention rate of 35.0% (95% CI, 19%-60%) and 73.8% (95% CI, 52%-92%) after 2 and 5 years, respectively. Fewer major reinterventions occurred in women with only 1 RFA-treated myoma (volume < 180 cm3, diameter <7 cm) than women with more than 1 RFA-treated myoma (>180 cm3, p <.01). The Kaplan-Meier estimates for reintervention in women with only 1 RFA-treated myoma with a volume < 180 cm3 were 13% (95% CI, 6-28%) and 26% (95% CI, 14%-45%) after 2 and 5 years, respectively. No patients with morphologic myoma characteristics underwent reinterventions. Conclusion: Ultrasound-guided RFA for uterine myomas is an alternative treatment option especially for women > 45 years of age with only 1 myoma (volume :<= 180 cm(3)) and warrants further evaluation. (C) 2017 AAGL. All rights reserved.