A variety of circumstances in which the scleral rigidity coefficient is reduced have been recorded.1-3 These include "thyrotropic ocular disease," high myopia, therapy with strong miotics, ocular surgery, and the water drinking test. Recent studies, however, have questioned the latter's effect on ocular rigidity.4-6 Consideration of the effect of the water drinking test on ocular rigidity assumes major significance when it is realized that this test is one of the most commonly employed in the early diagnosis of open angle glaucoma.7 Consequently, a detailed study of the effect of water drinking on ocular rigidity was undertaken, and is herein reported. Materials and Methods Normal and glaucomatous patients past the age of 45 and with refractive errors no greater than—2 to +2 D were obtained from the eye clinic of The New York Hospital-Cornell Medical Center. All normal patients had been followed in the eye clinic for