OBJECTIVE: To investigate the effects of four nonneutral neck positions on intracranial pressure. DESIGN: An alternating treatment design was used to investigate the effect on intracranial pressure of rotation of the head to the left and right, neck flexion and neck extension. Each experimental position was separated by a neutral recovery period. SETTING: Neurological intensive care units in two tertiary care centers in the southwestern United States. SUBJECTS: Ten patients whose intracranial pressure was being therapeutically monitored but who were not experiencing prolonged periods of elevated intracranial pressure. PROCEDURE: Each neck position was maintained manually by the research staff for 5 minutes. Intracranial pressure was recorded at 1-minute intervals throughout the 45-minute data collection period. RESULTS: Rotating the head to the right and left and placing the neck in flexion resulted in significantly higher intracranial pressure readings than the baseline neutral neck position or positioning the neck in extension. The highest individual intracranial pressures always occurred with the head and neck rotated or in flexion. CONCLUSIONS: These data support previous studies that indicated that a patient at risk for pathological increase in intracranial pressure should not be positioned with the neck in flexion or the head turned to either side.