A lesion of sporotrichosis shows a characteristic arrangement of the infiltrate in three zones: the central suppurative zone composed of polymorphonuclear leukocytes, the tuberculoid zone and the round cell zone. For investigating the pathomechanism of the suppurative zone formation, polymorphonuclear leukocyte chemotaxis to sporotrichin was assayed with the agarose plate method. Polymorphonuclear leukocytes in the patients with sporotrichosis showed an enhanced chemotactic index in comparison with that in the control subjects. However, there was no difference in non-specific chemotaxis to bacteria-derived substance between the patients and the control subjects.