&NA;Previous assessments of the value of sequential computed tomographic (CT) scanning in brain tumor patients have suffered from the heterogeneous nature of the study populations in regard to (a) pathology, (b) treatment plan, and (c) time of scanning. This report is based on the first 21 of 30 consecutive cases of glioblastoma multiforme entered into a cumulative high dose chemotherapy study. Each patient received a maximal surgical resection, 5800 to 6300 rads of radiation therapy, and BCNU (1,3‐bis(2‐chloroethyl)‐1‐nitrosourea) chemotherapy (beginning at 100 mg/m2/day × 3 days) every 8 to 10 weeks for the life of the patient. CT scans were obtained pre‐ and postoperatively and at each admission for chemotherapy; the scan at the time of the first BCNU course served as the postradiotherapy scan. Edema was present on 94% of the initial scans, and 94% of the tumors demonstrated contrast enhancement. In 70 instances it was possible to compare clinical status and an enhanced scan at the time of an adjuvant treatment. When the scan was improved or unchanged so was the patient (46 of 46), but worsening of the scan was accompanied by worsening of the patient only 62% of the time (15 of 24). Sequential CT scanning proved useful in (a) detecting the positive effect of a treatment plan in clinically stable patients; (b) detecting non‐tumor related causes of clinical deterioration; (c) detecting early treatment failure as a prelude to reoperation and/or a change in drug protocol before clinical deterioration; and (d) detecting asymptomatic complications of the treatment plan (i.e., a 20% incidence of ventricular enlargement). (Neurosurgery8:15‐19, 1981)