Neutrophil hyperfunction of Behçet's disease is in part regulated by genetical factors, especially related to HLA-B51 genes and by immunological abnormalities. Regarding the latter points, Behçet's disease worsens with abnormal regulation by gamma delta T cells and alpha beta T cells. Indeed, our own studies and those of other laboratories suggest that human heat shock protein may be one of the triggering factors for activation of both the gamma delta T cells and alpha beta T cells. These activated T cells may produce proinflammatory and/or inflammatory cytokines, and lead to tissue injury possibly via delayed-type hypersensitivity reaction, macrophage activation, and activation and/or recruitment of neutrophils. Here we discuss the crosstalk between the immune system and neutrophils in this disease.