In a previous study an attempt was made to determine the predominant types of bacteria in the colon in three patients with chronic ulcerative colitis. The symptomatology, x-ray and proctoscopic observations were in each case characteristic of the severe form of the disease. These patients had all been treated in the medical service for varying periods of time and were finally referred for surgical treatment because of progressive cachexia, anemia and persistence of local symptoms. In each case an end ileostomy was done. The bacteria in the isolated colon were then studied repeatedly at short intervals for several months. With the diversion of the fecal current, aerobic organisms began to diminish steadily in number and after a varying period of time the flora became almost entirely composed of nonsporulating anaerobes.1In the present study attempts were made to cultivate these organisms from the colon of seventeen additional cases and