Nuclear factor kappa-beta (NF-kappaB) is a critical transcription factor modulating the expression of many genes involved in the pathogenesis of psoriasis. SUMO4 is a negative regulator of NF-kappaB in the cell-signaling pathway. Two functional polymorphisms of the NFKB1 and SUMO4 genes have been found to be associated with the risks of some autoimmune-related diseases, but no published study has investigated the role of these polymorphisms in the etiology of psoriasis in the Chinese population. In this hospital-based, case-control study of 519 Chinese psoriasis vulgaris patients and 541 matched controls, we genotyped the NFKB1-94 ins/delATTG and the SUMO4 rs237025 A>G polymorphisms and assessed their respective associations with psoriasis vulgaris risk. We found that the genotype distribution of NFKB1-94 ins/delATTG polymorphism was statistically different between psoriasis patients and controls (P = 0.031). But the difference was not still statistically significant after correction for multiple comparisons. The frequency of wild WW genotype in psoriasis patients was statistically higher than that in controls (35.8 vs. 29.0%, respectively, P = 0.021). The W allele frequency in cases was also significantly higher than that in controls (59.7 vs. 54.1%, P = 0.008). Compared with the DD genotype, a significantly increased psoriasis risk was associated with the NFKB1 WW genotype (adjusted OR = 1.57, 95% CI = 1.10-2.24). In addition, the WW genotype frequency was also statistically higher in the psoriatic subgroups of onset age <or=40, PASI >20, male patients and sporadic patients than that in controls. But, no associations of the SUMO4 rs237025 A>G polymorphism with the susceptibility of psoriasis were detected. In conclusion, we found a marginal association between the NFKB1-94 ins/delATTG WW genotype and the increased psoriasis vulgaris risk and the association was more evident in the subgroups of onset age <or=40, PASI >20, male patients and sporadic patients in Chinese.