['Psoriasis is a common chronic inflammatory skin disease. IL23/Th17 is a newly confirmed pathway in psoriasis.', 'To investigate the gene-gene interactions in IL23/Th17 pathway underlying psoriasis.', 'A total of 299 single-nucleotide polymorphisms from 11 genes in IL23/Th17 pathway were genotyped on 1139 patients with psoriasis and 1694 controls. Multifactor dimensionality reduction and logistic regression algorithms were applied to explore the gene-gene interactions.', 'We found that there were a three-way interaction among IL21, CCR4 and TNF(χ(2) = 5.02(1), P = 0.025) and three pair-wise gene-gene interactions between IL12RB1 and CCR4(χ(2) = 11.66(4), P = 0.0201), IL22 and CCR4 (χ(2) = 11.97(4), P = 0.0176), IL12RB1 and IL6 (χ(2) = 7.31(1), P = 0.0069) in psoriasis.'] Do gene-gene interactions in IL23/Th17 pathway contribute to psoriasis susceptibility in Chinese Han population?