IT has been found that mammalian cornea is capable of eliciting an immunity reaction and of succumbing to it1. The following is a report of findings that human corneas possess A and B blood-group specific substances. Homogenized corneal tissue, obtained under sterile precautions by trephining the central portion of the cornea from cadavers, not later than 12 hr. after death, was used for adsorption of high-titred normal human sera. To 0.5 ml. of A, B and O sera, diluted 1 : 2 with normal saline, 0.5 ml. of corneal homogenate was added. The adsorption was carried out at 6° C. for 8 hr., the serum-cornea mixture being shaken every 15–30 min. The anti-4 and anti-B titre of the serum was examined against erythrocytes by the double serial dilution method, both before and after adsorption.