Subependymomas are rare, slow-growing tumors, the majority of which are found incidentally at postmortem examination. The authors retrospectively analyzed seven cases of symptomatic supratentorial subependymomas. Five were females and two were males, ranging in age at operation of 6-50 years (median 45). The follow-up period ranged from 1.5 to 8.3 years. Tumors were intraventricularly located as a lobulated mass with cystic changes: four in the frontal horn, two in the trigone, and one in the third ventricle. Moderate to marked enhancement was noted in two tumors of the trigone and in one tumor of the frontal horn on both CT scan and MR imaging. MR spectroscopy of a recurrent subependymoma demonstrated a higher Cho/Cr ratio of 2.66, compared with a Cho/Cr ratio (0.48) of a non-recurrent subependymoma. Angiography, which was performed in four patients, revealed no staining in two and delayed modest staining in two. Radiosurgery was performed in two patients but was ineffective. Five patients with gross total tumor resection showed no evidence of tumor recurrence to the last follow-up. The two subtotally resected trigonal tumors progressed two years after operation. No histological difference except MIB-1 index was noted between recurrent and non-recurrent cases. In conclusion, we suggest that subependymoma could show progressive biological behavior, especially in cases of markedly enhancing, irregularly contoured, large tumors located in the trigone. For symptomatic supratentorial subependymomas, gross total resection is the treatment of choice and radiation has little effect on tumor control.