BACKGROUND/AIMS: In chronic inflammatory conditions such as ulcerative colitis (UC), the migration of granulocytes and monocytes/macrophages from the circulation into the colonic mucosa is especially important in maintaining inflammation. The aim of this trial was to assess safety and efficacy of granulocyte and monocyte adsorption apheresis in patients with moderate-to-severe UC refractory to conventional drug therapies. METHODS: Twenty-seven patients with moderate (55.6%) to severe (44.4%) active UC refractory to conventional drug therapies who had no changes in their conventional therapy regimen in the past two weeks before the recruitment were enrolled in an open-label trial. Concomitant medications were allowed, and steroids were tapered down according to the clinical activity during the course. We used an adsorptive type extracorporeal column (Adacolumn(R); JIMRO, Takasaki, Japan), which selectively adsorb granulocytes and monocytes. Patients took five apheresis sessions, each with 60 minutes duration for 5 consecutive weeks. The primary efficacy variables were clinical disease activity, short inflammatory bowel disease questionnaire (SIBDQ), C-reactive protein (CRP), and endoscopic scores. These variables were scored at regular intervals, and analyzed at week 7 on an intention-to-treat (ITT) principles. RESULTS: At 7 weeks, 70.4% of patients showed overall improvement. Clinical disease activity (p<0.0001), endoscopic score (p<0.001), and the quality of life as assessed by SIBDQ (p<0.0001) were significantly improved after the therapy. In 56.3% of concomitant steroid users, tapering down or discontinuation of steroids was possible. Treatment was well tolerated, and no severe adverse events were observed. CONCLUSIONS: Adacolumn was very efficacious in patients with moderate-to-severe active UC refractory to conventional drug therapy, but further assessment is needed.