Aminopeptidase activity in the corneal epithelium and the conjunctiva of the albino rabbit eye was determined using L-leucine-, L-alanine-, and L-arginine-4-methoxy-beta-naphthylamide as substrates. This was compared with the aminopeptidase activity in the duodenum, jejunum, and ileum. The two ocular tissues were found to be 5-15% as active as the ileum in aminopeptidase activity. There was indirect evidence that the dominant aminopeptidase in the corneal epithelium is different from that in the conjunctiva, suggesting that further studies are warranted to investigate the possibility of delivering certain peptides systemically via the conjunctiva without simultaneously exposing the intraocular tissues to these peptides.