Implant compositions are disclosed consisting of a biocompatible carrier medium such as a saline or dextran solution and particles of collagenous material dispersed therein. The collagenous material is derived from tissue which has been milled to provide fragments of collagen fibers which preserve the architecture of the original fibers and their molecular structure. The collagenous material is also substantially free of non-fibrous tissue proteins, glycoproteins, cellular elements and lipids or lipid residues, and is non-cytotoxic. By suitable choice of particle size and concentration, the composition may be presented in injectable form or as a paste. The compositions are suitable for application in cosmetic and reconstruction surgery.