Collagen plays an important role in the final result of surgical intervention. For years, surgical catgut has been an irreplaceable suture material. Since the last decade, synthetic materials have gained ground. Healing of the intestinal wound is dependent on the repair of the epithelium, but the process takes place only if the collagen of the submucosal layer is such that epithelial cells can cover it. Surgical technique influences this process, and considerable progress is made by the use of mechanical devices as demonstrated by our own experiments. In the last years, a revival of collagen as biomaterial has been observed. Experiments in dogs showed that several applications are of interest. The matrix of processed natural collagen can support the repair of connective tissue in the host. In the near future, the competition between synthetic material and collagen in natural or reconstituted form will be continued and open new fields of research.