The pulmonary granulocyte content of the lung was quantified in patients with inflammatory bowel disease (IBD) after injection of 111In-labelled granulocytes and compared with patient controls, who, on the basis of their negative white cell scans, were not considered to have active inflammation. The mean ratios of lung:liver count rates per pixel on the posterior gamma camera image in patient controls was 0.34 (S.D. 0.16, n = 8) at 1-1.5 h after injection of the cells, and 0.29 (S.D. 0.14, n = 18) at 2-4 h. This ratio was higher in patients with active IBD at both imaging times: 0.45 (0.13, n = 13, P > 0.05) and 0.44 (0.1, n = 19, P < 0.001). Patients with inactive IBD also had increased ratios at both imaging times: 0.6 (0.14, n = 7, P < 0.01) and 0.54 (0.15, n = 12, P < 0.001), respectively. In a further group of 12 patients with active IBD, there was no correlation between the lung:liver ratio and the severity of the IBD as assessed by whole-body 111In retention at 4-6 days after labelled cell injection. These patients were treated for 3 weeks with an oral, non-absorbable corticosteroid, after which there was a significant decrease in disease activity but no significant change in the lung:liver ratio. Inflammatory bowel disease appears to be associated with abnormal pulmonary granulocyte accumulation. It is not apparently related to disease activity but may be the result of an associated pulmonary abnormality.