The authors determined whether vasoconstriction alters the ability of a noninvasive method (Finapres) of continuously measuring arterial blood pressure in the finger to function accurately. They compared the response of the Finapres to blood pressures determined simultaneously by an oscillometric technique (Dinamap) in six anesthetized patients. Vasoconstriction was detected from a photoelectric plethysmogram, which was recorded continuously from an adjacent finger. Vasoconstriction was defined as a decrease in amplitude to less than half of its highest value in one and the same patient. From the 378 paired blood pressure readings obtained in this study, 51% took place in such a vasoconstricted state. The authors found that diastolic and mean blood pressures in the finger were, on the average, 9 mmHg below those in the upper arm and that the systolic pressure was 7 mmHg above that in the upper arm. The authors concluded that the Finapres keeps functioning well during peripheral vasoconstriction and is a recommendable method to monitor arterial blood pressure in the finger.