Polyethylene tubes, closed at both ends with casting wax and with four perforations in the middle, were implanted subcutaneously in rats and evaluated as a research model simulating the root canal. As controls, wax bars and unperforated tubes were implanted. Attention was given to the reaction of the tissue surrounding the perforated empty tube, the tissue reaction to polyethylene and casting wax, and to the displacement of the tubes.