Meningiomas account for 18-20% of all intracranial tumours and often recur despite surgical resection. Hydroxyurea is under evaluation as adjuvant therapy of meningiomas. In the authors' initial report of 17 patients with meningioma, hydroxyurea demonstrated modest efficacy, with a median time to progression (TTP) of 80 weeks. In the current study, 21 patients with meningioma have been placed on hydroxyurea (20 mg/kg/day orally), with extended follow-up of the original cohort. Eighteen of 20 evaluable patients (90%) responded with stable disease ranging from 20 to 328 + weeks (median TTP 176 weeks; 11 patients censored). Five of the stabilized patients progressed after 20, 56, 36, 216 and 56 weeks, respectively. Two patients had progressive disease after 10 weeks. Toxicity was mainly haematological. Hydroxyurea has modest activity against meningiomas and should be considered for patients who are poor surgical candidates, have unresectable or large residual meningiomas, or have progressed after surgical resection or irradiation, or both.