The distribution of collagen fibronectin (FN) and laminin (LN) was studied in 18 skin lesions of patients with psoriasis and 7 normal human skin by PAP method.The Lc and c were present in the dermis of normal skin.In psoriatic lesions, the Ic and c stained darker than those in normal skin, and stained lightly in focal areas of upper dermis, periphery of blood vessels and regions with infiltration.The c, FN and LN distributed linearly in the basement membrane (BM), while they showed irregular thickness with segmental defects in the psoriatic epidermal BM.FN and LN were obviously absent in the top of the papillae, whereas they were net-like thickened on the two sides of the top of the papiliae.These results might be related to the increased synthesis of the fibroblasts and keratinocytes in the psoriatic lesions, but the focal light stain of Ic and c and the segmental defects of the components of the BM might be related to the phagocytosis of the inflammatory cells and the destruction of proteolytic enzyme released.