Contribution of transporter associated with antigen processing (TAP) genes to the pathogenesis of Behçet's disease (BD) was studied. Restriction fragment length polymorphic analysis of TAP genes was carried out in 46 Japanese patients with BD and 95 healthy subjects. There were no significant differences in allele frequencies of TAP1 and TAP2 genes between whole patients with BD and control population. No significant differences in the frequencies of TAP alleles were observed, when patients of BD with complete type or incomplete type were compared with control population, respectively. An allele frequency of TAP2C was, however, slightly but significantly high in patients with BD who had symptom of erythema nodosum (24.1%) as compared to the control group (11.6%). [p < .05, RR = 2.4]. The allele frequency of TAP2C was slightly high in HLA*B5101 positive patients with BD (28.6%) as compared to HLA*B5101 negative patients (10.9%), but the difference did not reach statistical significance. The absence of genotype TAP2B/C was observed in whole patients group, though it was present in control subjects (14.7%). [p = 0.003, RR = 0.06]. A genotype frequency of TAP2C/H was high in patients with BD who had symptom of skin lesions (7.5%) as compared to the control group (0.0%). [p = 0.03, RR = 15.4]. These results suggest the possibility that TAP molecule play some part in formation of skin lesion, such as erythema nodosum in BD in Japanese.