The usefulness of scintigraphy with 111In-oxine-labelled autologous leucocytes was investigated in 27 patients with inflammatory bowel disease (IBD): 16 with ulcerative colitis and 11 with Crohn's disease. Scans were performed 2-4 h (early scan) and at 24 h (late scan) after leucocyte reinjection. No false-negative results occurred in the early scan; however, in the late scan, 2 patients with Crohn's disease had a normal scintigram. A new index of activity (Il) based on the number and relative activity of abnormal 111In-leucocyte zones was used for scan quantitation. All patients with clinically active IBD had Il greater than or equal to 2. The scintigraphic index showed a significant correlation with the Harvey clinical index, especially in patients with ulcerative colitis. Our results suggest that an early scan (2-4 h) provides useful information in cases of IBD, and that Il greater than or equal to 2 is indicative of the degree of disease activity in such patients.