In the past decade there has been an increase in the use of plastics in surgery as suture material, for drains, as a replacement of bones and soft tissue defects, and, more recently, as blood vessel grafts. Some of the observers state that these synthetic materials are inert and incite no tissue reaction,2,7,16,22while others have reported reaction of varying degrees,3,15,21,23An evaluation is difficult because the response of the host will depend upon the site of implantation, degree of blood supply, motion, and the quantity of material implanted. The importance of removing the irritating plasticizers used in the manufacturing process has been previously emphasized.15,23 This paper represents a comparative study, under essentially the same conditions, of the tissue response to plastics that are being used commonly today. Method All the materials were washed thoroughly and boiled in a detergent solution, then rinsed and boiled in water.