Objective: to evaluate the long term effectiveness of presurgical therapy with GnRH analogues in patients who underwent hydrothermal endometrial ablation (HTA) for menorrhagia and assess the relationship between sonographically measured myometrium thickness and pelvic pain. Materials and Methods: A prospective randomized control study comparing 15 women (Group A) with presurgical subcutaneous triptorelin depot injection before HTA with controls (Group B, n=15). Inclusion criteria were: recurrent menorrhagia, uterus length < 12 cm, no previous hormonal therapy for at least six month, and family plan completed. Student’s t test was applied, as appropriate, to compare continuous variables. Proportion were compared with chi-squared. Results: After 12 months of follow-up, Group A showed a significantly lower (0% vs 20%; p = 0.03) failure rate after hydrothermoablation than the Group B and a generally higher successful rate at 24 and 48 months. The discomfort, evaluated with VAS, showed a mean value of 47.6 ± 15.9 (± SD); 96.7% of women reported a mildmoderate postoperative pain. No perioperative and late complications were recorded. Conclusions: Presurgical treatment with GnRH analogues seems to improve long term efficacy of HTA. Perioperative pelvic pain seems to not be affected by myometrium thickness.