The agglutination titers of Brachyspira pilosicoli ( B. pilosicoli ) and Brachyspira aalborgi ( B. aalborgi ) were examined in colitis patients with human intestinal spirochetes. Among three cases of colitis patients, the titer of B. pilosicoli was extremely high in two cases while the titer of B. aalborgi was extremely high in one case. These three cases had symptoms of colitis, such as watery diarrhea, and we diagnosed the case as Brachyspira- related colitis. These findings suggest that the agglutination titers of Brachyspira may be useful in cases of Brachyspira- related colitis. Severe symptoms, such as abdominal pain and diarrhea, were observed in cases with high antibody titer of B. aalborgi , as well as B. pilosicoli , indicating that B. aalborgi could also cause symptomatic colitis.