Head-of-bed (HOB) elevation is the standard of care for patients with intracranial pressure monitoring at risk for intracranial hypertension. Measurement of cerebral perfusion pressure (CPP) based on HOB elevation and arterial transducer position has not been adequately studied.This is a planned secondary analysis of prospectively collected data in which paired, serial arterial blood pressure (ABP), intracranial pressure, and CPP measures were obtained once per day for 3 days, with measures leveled at the tragus (Tg) and the phlebostatic axis (PA). The HOB position was recorded for all paired readings.From 136 subjects, ABP and CPP values were lower when the transducer was leveled at the Tg, compared with the PA (P < .001); these differences persisted regardless of HOB position.The difference in CPP when ABP is referenced at the Tg versus PA is not consistently attributed to HOB elevation.