The expression of the CD36 (OKM5) antigen was studied with the PAP technique on sections of skin from healthy subjects and of normal and diseased skin from patients with various skin diseases. In specimens from healthy subjects the antigen was found on vascular and perivascular structures and in some cases it was seen on cells of the acrosyringium. A net-like pattern of CD36 was observed in the upper part of the stratum spinosum in skin lesions of patients with psoriasis, lichen planus, pityriasis rosea, morbilliform drug reactions, necrobiosis lipoidica, lichen amyloidosus, Darier's disease and ichthyosis vulgaris. Expression of CD36 was also seen in the nonlesional skin just below the granular layer in 3 of 5 patients with factitial urticaria with immediate dermographism, but not in delayed dermographism or chronic urticaria. In ichthyosis vulgaris CD36 was also expressed in dendritic cells of the basal layer and in a patient with a graft versus host reaction it was recognized both on scattered keratinocytes and on dendritic cells in the epidermis. The role of the expression of the CD36 antigen in the skin is unknown. The activated cells might possibly serve as antigen-presenting cells and/or have a modulatory influence on an inflammatory reaction.