In 18 patients with dermatitis herpetiformis (DH) of whom 16 were HLA-DR3 positive and 14 had the HLA-B8, -DR3 haplotype, the frequencies of known mutations of the tumor necrosis factor α (TNF-α) and TNF-β genes were investigated using restriction fragment length polymorphism analysis and the single-strand conformational polymorphism technique. In DH, the phenotype frequency (28%) and allele frequency (0.58) of the rare TNF-β allele TNFB*1 were significantly increased (normal control 12.4% and 0.37). For the TNF-α promoter/enhancer polymorphism, the rare allele TNF2 was more frequent in DH patients (11%, 0.47) compared to controls (2%, 0.16). Since functional studies have associated the rare TNFB*1 and TNF2 alleles with a higher secretion of TNF upon activation in vitro, the predominance of these two ‘high-response’ TNF alleles in DH patients may represent a genetic basis for the chronic inflammatory response in the skin and mucosal tissues of patients