Serial cranial computed tomographic (CT) scanning and intracranial pressure monitoring were performed on 198 children with stage II and III tuberculous meningitis. The aims of the study were to document the course of tuberculous hydrocephalus during medical and surgical treatment, as well as the prognostic significance of parenchymal changes in the brain as demonstrated by CT. Lumbar cerebrospinal fluid pressure was monitored continuously for a 1-hour period in all patients on admission and at weekly intervals in patients with communicating hydrocephalus for the 1st month of treatment. Cranial CT scanning was done on admission and repeated in survivors after 1 month and again after 6 months of antituberculous therapy. The raised intracranial pressure of 112 children with communicating hydrocephalus, as demonstrated by air-encephalography, was treated medically (with daily acetazolamide and furosemide) for 1 month. Thirty-one children with noncommunicating hydrocephalus were referred for immediate ventriculoperitoneal shunting. No significant difference was found in the eventual ventricular size or clinical outcome between the two treatment groups. Lumbar cerebrospinal fluid pressure changes in the children with communicating hydrocephalus closely followed changes in the degree of hydrocephalus during the course of treatment. The main cause of permanent neurologic disability was basal ganglia infarction, which occurred unilaterally in 21% and bilaterally in 10% of patients on admission and developed in a further 22% of children during treatment. A prominent subarachnoid space, which was seen on the CT scan of 36% of patients after the 1st month of treatment and which reverted to normal, probably relates to the poor nutritional state of these patients on admission.(ABSTRACT TRUNCATED AT 250 WORDS)