Résumé : OBJECTIVE: To examine the long-term (4-year) safety and tolerability of dutasteride in the treatment of symptomatic benign prostatic hyperplasia (BPH). PATIENTS AND METHODS: Patients who completed the double-blind phase of three dutasteride Phase III studies were eligible to enter a 2-year open-label extension, during which all patients received dutasteride 0.5 mg. Safety was assessed, including adverse-event reporting, clinical laboratory assessments, yearly physical examinations, and vital sign assessments. RESULTS: In all, 2340 patients entered the open-label phase, 1188 of whom previously received dutasteride during the double-blind phase of the study. The most common drug-related adverse events (occurring in ≥1%) were effects on sexual function, which decreased with a longer duration of therapy. Gynaecomastia was reported in a small percentage of men throughout the 4-year study period. The incidence of individual sexual functional adverse events that led to withdrawal was ≤1% (0.3-1.0%) during the 4-year study period. Dutasteride had no relevant effects on vital signs or clinical laboratory variables. CONCLUSION: These data show that dutasteride is well tolerated during long-term use for the treatment of symptomatic BPH. © 2005 BJU International.