We succeeded in the simultaneous isolation of Brachyspira (B.) aalborgi and B. pilosicoli from a patient with ulcerative colitis. B. pilosicoli grew quickly and formed colonies within 7 days, while the growth of B. aalborgi was very slow and took over 21 days. Simultaneous isolation of B. pilosicoli and B. aalborgi from a common specimen is generally recognized to be difficult, mainly due to differences in their growth requirements and the growth rates. However, we succeeded in isolating both species from a patient with ulcerative colitis and this is first evidence. The present results suggest that ulcerative colitis may be caused by simultaneous infection with B. pilosicoli and B. aalborgi.