We examined the intraoperative use of jugular venous bulb catheters in 100 consecutive patients undergoing neurosurgical procedures. The catheters were successfully placed after induction of anesthesia in 99 patients using an aseptic technique. The efforts were abandoned after four attempts in the remaining patient. The mean time of insertion was 94 s (SD 108, range 15- 420). Carotid artery puncture on two occasions controlled by firm pressure was the only complication. Arterial blood pressure, PaCO2, PaO2, and jugular venous bulb oxygen saturations (SjVO2) were intermittently measured at set intervals throughout the operation. We defined cerebral venous desaturation as 1) none (SjVO2 < 50%), 2) mild (45% < SjVO2 < 50%), and 3) severe (SjVO2 < 45%). We graded the usefulness of the catheter as 1) not useful (NU), SjVO2 > 50% and PaCO2 > 25 mm Hg; 2) useful (U1), SjVO2 > 50% and PaCO2 < 25 mm Hg; intervention, no increase in PaCO2; 3) useful (U2), SjVO2 < 50% and PaCO2 < 25 mm Hg; intervention, increase PaCO2 to improve SjVO2; 4) useful (U3), SjVO2 < 50% and PaCO2 > 25 mm Hg; intervention, nonventilatory action to increase SjVO2 (e.g., infusion of mannitol). Mild desaturation was detected in 24 patients and severe desaturation was present in 17 patients. We found SjVO2 monitoring to be useful in 60 of 99 patients studied. It was useful for detecting and treating cerebral venous desaturation in 13 of 18 patients with intracranial hematomas (subdural, epidural, and intracerebral hematomas), 9 of 18 patients with intracerebral tumors, 27 of 45 patients with cerebral aneurysms, and 6 of 8 patients with other intracranial pathology. It was of no benefit in patients (n = 10) with arteriovenous malformations. We conclude that intraoperative monitoring of SjVO2 is feasible, practical, and may be beneficial for patients undergoing neurosurgical procedures, both for detecting and treating cerebral venous desaturation, and for calculating the cerebral arteriovenous oxygen content difference (AVDO2). Furthermore, given the low rate of complications in experienced hands, its use as a routine monitor during neurosurgical procedures should be further explored.