Examination of colonic enterocytes inoculate with pure culture of S. hyodysenteriae by phase-contrast microscopy revealed that only few spirochaetes adhere to epithelial cells. S. hyodysenteriae was observed to be highly motile, showed corkscrew-like movement which might suggest that bacteria were trying to penetrate and damaged the host cells. The pattern of motility provide evidence of a chemotaxis. Supernatant of S.hyodysenteriae lysate were found to cause CTE in CHO, Vero and PK-15 culture. This support the hypothesis that damage is consistent with the presence of toxin. Inhibition activity of serpulinas hemolysin preparation with streptolysin S inhibitors confirms the suggestion that the mechanism by which S. hyodysenteriae toxin effects the cells seems to be similar to the action of streptococcal toxin S.