The origin of the wound fibroblast and macrophage was studied in a patient following bone marrow transplantation, using sex chromosome markers. Fibroblast-like cells emigrating from explants of a 5-day-old skin wound had the host karyotype, whereas macrophages had donor markers. These results suggest that the wound fibroblast in man is of local tissue origin, whereas wound macrophages are derived from haemopoietic tissue.