Intraocular pressure (IOP) response to hanging completely head-down (inversion) was measured in 26 healthy young subjects. Systolic and diastolic blood pressure (BP) were also recorded. From the standing position, subjects were rotated 180 degrees and suspended by the ankles from a gravity inversion device. IOP and BP were measured in the standing position, immediately upon inverting, 3 min after inverting, immediately on return to the standing position and 3 min later. Subjects remained at rest during the test. Mean standing right eye IOP of 16.4 mm Hg and left eye IOP of 15.9 mm Hg increased to 34 and 31 mm Hg, respectively. Mean standing BP of 110/77 mm Hg increased to 130/90 mm Hg. Both IOP and BP remained elevated during inversion and decreased to near original values on return to the standing position. IOP significantly increases when the posture changes from standing to hanging completely head-down.