Patients with renal disease or diabetes mellitus often have an acquired perforating disease of the skin develop that is characterized by hyperkeratotic papules with transepidermal elimination of degenerated material, including collagen or elastic fibers. There is disagreement regarding the most appropriate name for this disease. The pathologic process has been identified by various authors as reactive perforating collagenosis, elastosis perforans serpiginosa, perforating folliculitis, or Kyrle's disease. We have seen four patients with renal disease and/or diabetes whose skin biopsy specimens demonstrated combined transepidermal elimination of both collagen and elastic fibers. This finding is not characteristically seen in any of the previously defined perforating diseases. Since the histologic findings vary greatly in different lesions from different patients with renal disease, we recommend referring to this process as "acquired perforating dermatosis." It is best not to create a new category of perforating disease or to say that a given patient has one of the other four diseases based on random sampling of only a few lesions.