Seventy-three patients with subcortical or deep-seated brain tumours have been operated on with the aid of intraoperative ultrasonography. Forty-one had metastases and thirty-two primitive neuroepithelial neoplasms. In all cases ultrasonography allowed an easy and precise localization of the tumours. The removal was gross total in 45 cases (61.6 per cent), subtotal in 17 (23.3 per cent) and partial in 11 (15.1 per cent). Preservation or improvement of the Karnofsky Performance Status was obtained in 63 patients (86.3 per cent), with a morbidity and mortality rate of 11 and 2.7 per cent respectively. Our results indicate that ultrasound guided microsurgery represents a handy, reliable and relatively low risk procedure for the treatment of intra-axial brain tumours.