Simultaneous monitoring by cerebral oximetry and electrophysiological methods (electroencephalography and electrocorticography) was performed in 21 patients with arterial cerebral aneurysms during direct intracranial interventions, endovascular interventions, and Matas' test. Electrophysiological methods are sufficiently accurate indicators of cerebral ischemia even at a functionally reversible level. The results of simultaneous monitoring were similar in 80% cases, indicating cerebral ischemia even at functionally reversible level, which was detected by both electrophysiological methods and cerebral oximetry. Variously directed shifts were detected in 4 cases; the causes are discussed. Cerebral oximetry detects cerebral ischemia with a sensitivity similar to that of electrophysiological methods. The method does not depend on temperature or anesthetics. Limitations of the method are due to its local application.