A valve implant for glaucoma incorporated upper and lower intraocular pressure limits for outflow. The device consisted of an open Supramid tube sealed to a Silastic tube with a slit valve. The valve implants had opening pressures of 11 to 16 mm Hg and closing pressures 1 to 3 mm Hg lower. A surgical technique was developed in monkey eyes and applied later in modified form to three patients with glaucoma. In four of seven monkey eyes the implants remained in place and were patent for over one year. Follow-up studies were carried out for over six months in the three patients. In two patients the valve implants were functioning with controlled intraocular pressures. In one patient the implant migrated posteriorly. This was replaced by using a new valve and a buried fixation suture and has since functioned without problem. The valve implants were well tolerated and offered possibilities for predictable intraocular pressures after glaucoma surgery.