During the past five years the successful use of synthetic vascular prostheses of nylon, Orion, Dacron, Ivalon, and Teflon has stimulated investigators to try fabrics of these same materials for the repair of tissue defects of the abdomen and chest wall. With the possible exception of Teflon, these fabrics have had to be removed, in the presence of infection, and this has been a major deterrent to their use clinically. Another problem has been that of obtaining a weave porous enough to allow abundant growth of fibrous tissue through the graft without sacrificing tensile strength and "body," so essential in this type of prosthesis. This is particularly true of Teflon, which, although it has desirable physical properties, cannot be woven into a satisfactory monofilament mesh. Marlex polyethylene is a new plastic, recently developed by Phillips Petroleum Company, Bartlesville, Okla. It is a high-density polyethylene produced from ethylene gas in a