Combination chemotherapy with procarbazine, CCNU and vincristine (PCV) may be effective in patients with recurrent glioma. Response monitoring is mandatory, but radiological response evaluation is often difficult. We evaluated Thallium-201 (201Tl) SPECT as a response parameter in ten patients treated with intensive PCV chemotherapy for recurrent glioma. 201Tl-SPECT studies showed early changes (decreasing volume and intensity) in nine patients and these changes were more pronounced than radiological findings. 201Tl-SPECT results after completion of chemotherapy seemed to correlate with clininal findings during follow up. We conclude that 201Tl-SPECT may contribute to the assessment of response in patients treated with PCV chemotherapy for recurrent glioma.