Objectives: Elucidate the interaction of polymers used for specific implants with the physiological environment; explore specially prepared polymers and design features with respect to their suitability and performance in a variety of contexts. Methods employed: Basic polymer composition is carefully controlled and modification of cross-linking systems is employed. Rheological properties are studied as a function of cross-linking. Implants are examined after removal for lipid absorption, protein deposition, changes in surface-free energy, and alteration of physical properties. Observations include SEM, infrared spectroscopy, contact angle measurements, energy dispersive x-ray analysis and atomic absorption spectroscopy. Flow characteristics and pressure gradients across heart valve implants are studied in vitro in test apparatus. Major findings: Ten heart assist devices with segmented polyurethane blood contacting surfaces were implanted in calves for up to 35 weeks. No lipid absorption was observed; physical strength remained stable; surfaces developed a biocompatible layer of protein. Six additional assist devices have been implanted with similar results; two total heart implants have been achieved. A series of ventricular-aortic by-pass devices functioned satisfactorily for periods up to 17 weeks in dogs with negligible blood damage. Clinical trials are now being planned. Six segmented polyurethane covered polypropylene poppets housed in standard "Starr-Edwards 3M" cages have been implanted in calves. One was electively removed after one year; no obvious physical or chemical changes occurred and there was no evidence of injury to the animal. Significance: Physiologically compatible polymers with enduring strength are needed for such applications as heart valves, heart assist devices, vascular implants, and subcutaneous uses. Proposed course: (1) Extend experimental studies to further characterize the surface and bulk properties of polyether urethanes and more specifically determine its interactions with blood and subcutaneous tissue. (2) Study new designs of tricuspid heart valves for acute and chronic use. (3) Study new designs of drains to be used in the eye to treat glaucoma.