Summary: To investigate the role of Interleukin-17 (IL-17), Interferon-gamma (IFN-γ), and macrophage inflammatory protein-3 alpha (MIP-3α) in the pathogenesis of psoriasis, reverse transcriptase-polymerase chain reaction (RT-PCR) was used to semi-quantitatively analyze the mRNA expression of IL 17, IFN-γ, and MIP-3α in 31 psoriatic lesions and 16 normal skin tissues. The results showed that the mRNA of the three cytokines was present in all specimens. And the expression level of IL-17 mRNA in skin lesions was 1. 1416±0. 0591, which was significantly higher than that in normal controls (0. 8788±0. 0344, P＜0. 001). The expression levels of IFN-γ mRNA were 1.1142±0. 0561 and 0. 9050±0. 0263, respectively, with significant difference(P＜0. 001). And the expression levels of MIP-3α mRNA in psoriatic lesions was 1. 1397 ± 0. 0521, which was markedly higher than that in normal controls (0. 8681±0. 0308, P＜0. 001). These findings indicate that up regulated expression of IL-17, IFN-γ, and MIP-3α might be involved in the pathogenesis of psoriasis.