Introduction The antidiuretic effect produced by the vasopressor hormone of the posterior pituitary lobe—β-hypophamine; vasopressin U. S. P.—is well known.1 It promotes the resorption of water by its action on the renal tubules. Interest in this hormonal effect was stimulated by a desire to increase the hemodilution following water drinking as a provocative test for glaucoma. It was hoped that the more intense and uncompensated decrease of osmotic pressure of the plasma produced by the administration of vasopressin with the water might lead to more consistent changes and a higher percentage of significant rises in intraocular pressure in glaucoma suspects. Meves2 reported that systemic Pituglandol (containing vasopressin and oxytocin) given with the water-provocative test produced a greater and more prolonged rise in ocular tension than could be obtained with water drinking alone. He also cited two patients with glaucoma who had negative water-provocative tests, but positive tests when