In 77 normal and 65 glaucomatous eyes the influence of body position on the intraocular pressure was studied, using the pneumatonograph. The pressure increment when changing from the seated to the supine position averaged 2.9 mm Hg in normal eyes and 3.9 mm Hg in glaucomatous eyes. The pressure increase occurred immediately upon lying down and was reversible after returning to the seated position. Comparative measurements with the Goldman tonometer in the seated position showed good agreement with the results obtained by the pneumatonograph. The Schiotz tonometer did not reliably reveal the true supine intraocular pressure. The postural response (seated to supine) showed considerable variation in individual normal and glaucomatous eyes, and it did not correlate consistently with the intraocular pressure in the seated position. It should be taken into account that the results in the glaucomatous eyes were obtained while the patients were on glaucoma medication. In a series of six lowtension glaucomatous eyes the postural response was significant as a probable pathogenetic factor in that disease, because the intraocular pressure could rise from a normal to a glaucomatous level upon changing from the seated to the supine position.