An adjuvant chemotherapy regimen consisting of procarbazine, MCNU, and vincristine (PMV) was evaluated for the treatment of malignant oligodendroglial tumors. Ten patients with histologically proven oligodendroglial tumors were treated with PMV therapy and the effectiveness was assessed using magnetic resonance imaging. Four patients with primary tumors underwent PMV after radiation therapy, and six patients with recurrent tumors were treated using PMV only. Tumor response was defined as radiological evidence of mass size change after completion of three courses of PMV. Complete or partial responses (more than 50% reduction in tumor mass) were noted in six patients, and tumor growth stabilized in four patients. In particular, inhibition of tumor growth using PMV was achieved in three patients with recurrent oligodendroglial tumors, despite the initial response after chemoradiation therapy (interferon-β, MCNU, radiation) or nitrosourea chemotherapy (ACNU, MCNU). This PMV regimen (a modified PCV regimen using drugs available in Japan) is effective for treating malignant oligodendroglial tumors despite recurrence after other initial treatment procedures.