The dynamic changes in regional cerebral blood flow (rCBF), induced by a developing intracerebral hematoma, were studied in eight anesthetized monkeys. Hematomas were generated by allowing femoral arterial blood to enter the caudate nucleus via a stereotactically implanted needle. Intracranial pressure peaked at 51 +/- 8 mmHg at 3 minutes after the ictus, and remained high throughout the 3-hour procedure. Cerebral blood flow was significantly reduced in all brain regions for 1 hour after the ictus. The lowest rCBF values were recorded in the immediate clot penumbra and were below threshold levels for ischemic neuronal damage for 90 minutes after the hemorrhage.