Aims : To assess the clinical significance of faecal calprotectin levels (a neutrophil protein) in patients with ulcerative colitis (UC). Methods : 25 patients with UC provided stool samples for calprotectin assay and the amount of calprotectin was related to UC disease activity index in each patient. Of 25 patients 4 with prednisolone refractory UC received 10 granulocyte and monocyte adsorption apheresis (GMCAP) sessions of 60 minutes duration, flow rate 30mL per minute for 10 consecutive weeks. Results : Calprotectin level in consecutive faecal samples from three patients was stable. However, increased calprotectin levels were significantly (p<0.005) associated with Matts' s endoscopic index, reflecting the level of colorectal inflammation. The 4 patients who received GMCAP therapy had a clinical activity index < 2 at week 7, the calprotectin level declined with improving Matts' index. Conclusions : Assay of faecal calprotectin holds promise as a sensitive biomarker to identify colorectal inflammation.