Proctase-treated collagen solutions and gels were implanted in the anterior chamber and vitreous of 72 rabbit and 27 monkey eyes and their appearance, fate, and effects on surrounding tissue determined. All implants were well-tolerated, although an initial inflammatory response to collagen implants in monkeys exceeded that seen in controls. Ultraviolet irradiation was used to produce collagen gels and to prevent in vivo aggregation of collagen solutions. These implants retained their gel-like structure in vivo and were absorbed from rabbit anterior chambers in two weeks and from monkey vitreous in two months. All implants were totally absorbed without damage to the eyes.