The tissue reaction to implanted monofilamentous and multifilamentous polypropylene mesh was compared in samples removed at operation from the perivaginal area of a 58 year old patient. The fibrils of both were surrounded by collagenous connective tissue, collagen types I and III, and proteoglycans. Smaller, less compacted bundles were seen in the vicinity of the monofilamentous mesh than around the multifilamentous mesh, and in addition, a greater number of inflammatory cells and larger multinucleate giant cells were seen apposed to the monofilamentous mesh. Following this, eight rats were implanted with multifilamentous synthetic polypropylene tape and examined at two, four, six and eight weeks after surgery. Macrophages and multinucleated giant cells were seen in the immediate vicinity of the fibrils, while fibrovascular connective tissue surrounded the implantation site. These observations do not support the prevailing hypotheses that macrophages cannot penetrate between the fibrils of multifilament tape. They do suggest that differences in tensile strength may be present in the artificial neoligaments created by the two tapes.