• The pressures of the episcleral veins of 20 normal patients, 29 patients with ocular hypertension, and 22 patients with treated primary open angle glaucoma were measured by an air pressure chamber device mounted on a slitlamp. The episcleral venous pressures (EVPs) of the patients with ocular hypertension were found to be significantly lower than those of the patients with glaucoma and the normal patients. The EVP was also found to be significantly negatively correlated with the ocular pressure (OP), so that the EVP decreases as the OP increases. A logarithmic model of the form EVP = 19.41 - 3.65 1n OP was found to best fit the data.