In the preceding paper2 evidence was presented that the maintenance of intraocular tension of a normal rabbit eye was not dependent upon the carbonic anhydrase activity of the anterior uvea. The present study was undertaken to determine whether the inhibition of carbonic anhydrase activity of the anterior uvea by the intravenous and subconjunctival administration of acetazoleamide ( Diamox; 2-acetylamino-1,3,4-thiadiazole-5sulfonamide) affected the concentration of bicarbonate ions in the aqueous humor. Our results show that the elaboration and active transfer of bicarbonate ions into the aqueous humor are not mediated by the carbonic anhydrase of the anterior uvea of the normal rabbit eye. EXPERIMENTAL STUDY The recent observations of Kinsey3 that the concentration of bicarbonate ions in the posterior chamber of the rabbit eye is not only greater than that in the plasma but also greater than that in the anterior chamber were offered in support of Friedenwald's postulate4 that