Subependymomas of the fourth ventricle are generally considered incidental postmortem findings, and have received scant attention from neurosurgeons. The authors present a surgical series of 12 cases of this disorder diagnosed over a 13-year period. The clinical and radiological findings were reviewed and correlations made with pathological studies. The subependymoma is a histologically benign tumor that tends to be calcified. It has a predilection for the fourth ventricle and a peak incidence in the fifth decade of life. It is usually of considerable size with extensive attachment at the time of its detection, and is associated with significant surgical morbidity. The authors believe that magnetic resonance imaging may be the best method of investigation. Intraoperative disturbance of circulatory or respiratory control should suggest to the surgeon that the operation can be abandoned. A laser or ultrasonic aspirator may be very helpful in removing these tumors. Postoperative care must include monitoring for apnea.