The usefulness of 99mTc-nanocolloid for the assessment of localization and disease activity of colitis in patients suffering from inflammatory bowel disease (IBD) was investigated in 10 patients. Results of 99mTc-nanocolloid scintigraphy were compared with Indium-111 autologous granulocyte scintigraphy and the activity index according to Van Hees. In none of the patients a true positive result of the 99mTc-nanocolloid scintigraphy was encountered, while 111In-granulocyte scintigraphy was positive in 7 of 10 patients with active disease. Radioactivity became visible in the small bowel starting 2 h after injection of 99mTc-nanocolloid most likely because of excretion by the liver of degradation products of the radiopharmaceutical. The authors conclude that despite a previous communication 99mTc-nanocolloid cannot replace 111In-granulocytes for the assessment of IBD patients with active colitis.