Collagen membrane preparations were manufactured with the aim of enhancing wound healing following periodontal surgery. In order to clarify effects of different concentrations of collagen on wound healing, a basic study was performed. Solutions containing 0.5%, 1.0%, and 1.3% atelocollagen were treated with hexamethylenediisocyanate (HMDIC) for cross-linking, and collagen membranes were prepared with each solution. Periodontal flap surgery was performed on the palatal gingiva beside the maxillary first molar teeth in rats. The root surface of the tooth was exposed and curretted. Then, a piece of atelocollagen membrane was implanted. The healing of the wound was studied histologically and the following findings were made. (1) Apical migration of the junctional epithelium occurred within 2 weeks postoperatively. (2) The implantation of atelocollagen membrane significantly reduced the apical migration. (3) The apical migration of the epithelium did not vary with collagen concentration.