To investigate the possible role of interleukin (IL)-10 and IL-12 in the pathogenesis of psoriatic lesions and to supply theoretical basis for the gene therapy for psoriasis, the expression of IL-10 and IL-12 P35, P40 mRNA in 12 cases of psoriatic lesions and 6 normal skin tissues was detected by using RT-PCR technique. The results showed that the expression of IL-10 mRNA in the psoriatic lesions was significantly lower than that in the normal skin tissues (P < 0.001). The expression of IL-12 P35 was positive both in the psoriatic lesions and in the normal skin tissues. IL-12 P40 mRNA was expressed positively only in the psoriatic lesions but negatively in the normal skin tissues. It was suggested that IL-12 might take an important role in the occurrence and progression of psoriasis, but IL-10 might have certain role in the regression of psoriasis.