We studied the changes in the propofol concentration in the cerebrospinal fluid (CSF) in 14 patients, undergoing elective intracranial procedures, who were anesthetized with propofol administered by target-controlled infusion. During anesthesia, fentanyl and cisatracurium were administered as required. After intubation of the trachea, the lungs of the patients were ventilated to normocapnia with an oxygen-air mixture (FIO(2) = 0.33). Arterial blood and CSF samples (from an intraventricular drain) were collected between 90-180 min after the induction of anesthesia. Blood propofol concentrations were stable, between 5.0 +/- 1.89 and 4.5 +/- 1.7 microg/mL (mean +/- SD). There was a significant decrease in the CSF propofol concentration, from 52.2 +/- 35.01 ng/mL at 90 min to 28.6 +/- 21.9 ng/mL at 150 min (P < 0.05). The CSF propofol concentration at 180 min (21.4 +/- 14.0 ng/mL) was not significantly different from the concentration at 150 min. Some possible reasons for this decrease after commencing continuous intraventricular drainage are discussed. CONCLUSIONS Propofol concentrations in the cerebrospinal fluid in neurosurgical patients Propofol concentration in cerebrospinal fluid of investigated patients decreased significantly after starting intraventricular drainage, despite relatively steady blood propofol concentrations. These results supplement the limited information about propofol pharmacokinetics in the human central nervous system.