In order to study the expression of interleukin-22 (IL-22) and S100A7, A8, A9 mRNA in the skin lesions of patients with psoriasis vulgaris and their relationship, the biopsies were taken from skin lesions in 35 patients with psoriasis vulgaris and the skin of 16 normal controls, and the expression levels of IL-22 and S100A7, A8 and A9 mRNA were detected by semi-quantitative RT-PCR. The results showed that (1) IL-22 and S100A8, A9 mRNA were positively expressed in the psoriatic skin lesions but negatively expressed in the normal controls; The expression level of S100A7 was (1.133+/-0.040) in the psoriatic skin lesions, significantly higher than that in the normal controls (0.744+/-0.037, P<0.01). (2) There were significantly positive correlations between the expression of IL-22/S100A7 mRNA, IL-22/S100A8 mRNA, IL-22/S100A9 mRNA in the psoriasis vulgaris (r(1)=0.543, r (2)=0.774, r(3)=0.621, P<0.01). It was concluded that IL-22 and S100A7, A8, A9 might play important roles in the occurrence and progression of psoriasis.