The effects of radiochemotherapy on blood flow, blood volume, and consumption of oxygen and glucose in tumor tissue and normal brain were studied by positron emission tomography. Thirteen patients with cerebral gliomas were included, and they were examined before, during, and within approximately 1 month after the therapy. The 15O-labeled gas steady state inhalation and the 18F-fluorodeoxyglucose methods were used. After the therapy, glucose consumption and blood volume decreased (p less than 0.03) in the tumoral tissue. In the structurally (CT) normal gray matter, blood flow, blood volume, and oxygen consumption did not show any significant changes; oxygen extraction fraction, glucose consumption, and glucose extraction fraction, however, decreased significantly (p less than 0.05, less than 0.02, and less than 0.03, respectively).