Abstract Tumor necrosis factor (TNF)-α is one of the proinflammatory cytokines and immunomodulators, and has an important pathogenetic role in psoriasis. The TNF-α gene ( TNFA) is in the human leukocyte antigen (HLA) class III locus on chromosome 6, which might be related to the pathogenesis of psoriasis. It has been suggested that some polymorphisms of the TNFA gene promoter, especially G to A conversions at nt-238 and -308 (TNF-238A and -308A), may be associated with psoriasis in Caucasians. We investigated single nucleotide polymorphisms (SNPs) of the TNFA gene promoter in Japanese psoriasis patients, including 18 with psoriasis vulgaris (PsV), 11 with psoriatic arthritis (PsA), two with generalized pustular psoriasis (GPP), and six with GPP with arthritis. The DNA fragment of the TNFA gene from nt-400 to -69 was amplified by polymerase chain reaction (PCR) and the products were sequenced. Although TNF-238A and other polymorphisms were not found in PsV and psoriatic arthritis patients, one male patient with GPP and PsA had TNF-308A. This suggests that TNFA gene promoter polymorphism in the region examined is less associated with the pathogenesis of psoriasis in Japanese patients, however there might be the possibility that TNFA gene promoter polymorphism is associated with GPP. Further investigation will be required to prove this.