The involvement of endothelial cells and vascular smooth muscle cells in the initiation, formation and development of aneurysmal dilatation of coronary arteries in Kswasaki disease(KD) have been emphasized. It has been thought that specific growth factors may have an effect on anintimal thickening and vascular dysfunction. Plateletderived growth factor(PDGF) is reported to be involved in various clinical situations such as wound healing,atherogenesis,embryogenesis, and infectious diseases. In this regard, we explored the localization of PDGF in KD. Sections of skin biopsies from 8 KD patients were investigated using the mouse anti-human PDGF monoclonalantibody. Samples obtained in the acute stage were stained with ABC technique. As a result, PDGF was detected in the dermis and epidermis. The prominent staining for PDGF was found in the endothelial lining of dilated qapillaries and in the cytoplasm of macrophages~ Positive staining for PDGF was particularly associated with macrophage infiltrates. In conclus{on, it is postulated that PDGF may play an importantrole in the initiation and/or healing process of vasculitis, and skin lesion in KD. { 28