This study was to clarify whether Behcet's disease (BD) could be classified into the spondyloarthropathy (SpA) complex. It was undertaken on 58 patients with BD (BD group), 56 patients with SpA (SpA group), and 3 patients who concurrently satisfied the criteria for BD and SpA (BDSpA group). The clinical parameters and known susceptible HLA antigens were compared between BD group and SpA group. In addition, 3 patients in BDSpA group were reviewed. The prevalence of definitive sacroiliitis (SI) in BD group and SpA group was 46.4% and 5.2%, respectively. However, none had a definitive SI in healthy controls. Enthesitis was observed in 3.4% of BD group and in 50% of SpA group. The patterns of eye involvement were different between these two groups. HLA-B27 was negative in all 49 patients of BD group, whereas it was positive in 67.9% of SpA group. The prevalence of HLA-B51 was 51.7% in BD group, and that in SpA group was 21.4%. One patient in BDSpA group was considered to have concurrent BD and ankylosing spondylitis (AS). Another patient was closer to AS, and the third to BD. Conclusively, it seems that BD could not be classified into the SpA complex.