This series reports a pilot study of chemotherapy conducted for newly diagnosed and relapsing patients with oligodendrogliomas and oligoastrocytomas. Twenty-three patients with clinically or histologically aggressive tumours were eligible to receive procarbazine CCNU and vincristine (PCV) chemotherapy followed by radiotherapy in previously non irradiated patients. Sixteen (69%) responded to chemotherapy with complete responses in two patients and partial responses in 14. Previously irradiated patients were as likely to respond to PCV as those previously non irradiated. An over 1-year history of seizures was the main clinical prognostic factor of response. All toxicities were manageable and no treatment related deaths occurred. Chemotherapy is an effective treatment in aggressive oligodendrogliomas. Further studies must assess the role of chemotherapy in the multidisciplinary management of oligodendroglioma.