We investigated the effect of a forcible eyelid squeeze (two-second squeeze and two-second rest) over one minute, on intraocular pressure in volunteer groups of normal volunteers, ocular hypertensive and glaucoma patients, and those with a family history of glaucoma. The normal volunteers fell into two groups: responders and nonresonders, with the responders showing about a 2-mm Hg decrease and the nonresponders a small increase in intraocular pressure. It was possible to arrange the groups into an order dependent upon the change in intraocular pressure induced by eyelid squeezing; normal responders (-1.98 mm Hg), family history of glaucoma (-0.48 mm Hg), ocular hypertensive patients (-0.07 mm Hg), normal nonresponders (+ 0.04 mm Hg) and glaucoma patients (taking medication) (+ 0.25 mm Hg). Correlation of disease entity with other ocular factors such as intraocular pressure and total outflow facility was poor.