The permeability of the blood-aqueous barrier in rabbits was investigated by determining the aqueous and blood urea concentrations The ratio in normal rabbits was 0.90. When urea was injected in doses of 1.2 g./kg. the ratio, in 1.5 hrs., was 0.63. Breakdown of the blood-aqueous barrier by a standard corneal burn by NaOH caused the ratio to rise to 1.05. The administration of Ca gluconate (I), rutin (II), or adrenosem (III) dropped the ratio to 0.93, 0.78, and 0.79, resp., the differences being statistically significant. The permeability of the barrier is greatly increased with a breakdown. II and III have a favorable therapeutic effect while I is of limited value.