Sickled erythrocytes leave the anterior chamber of human and monkey eyes by several mechanisms: intracameral and intratrabecular hemolysis and phagocytosis; entry into and phagocytosis within the iris and ciliary body; and passage into Schlemm's canal. Sickled erythrocytes used as biologic tracers allowed definite confirmation, for the first time in the human, that intracameral erythrocytes can enter Schlemm's canal in the orthograde direction. Erythrocytes appeared to traverse the inner wall of Schlemm's canal through the cytoplasm of individual endothelial cells, rather than between adjacent endothelial cells -- a mechanism similar to that employed by red and white blood cells elsewhere in the body. Although some sickled erythrocytes did pass into Schlemm's canal, considerable obstruction appeared to occur at the corneoscleral meshwork, juxtacanalicular connective tissue, and inner wall of Schlemm's canal, caused largely by the elongated, rigid nature of the sickled cells. Total blockage of Schlemm's canal was not observed.