To study the possible alteration of mucosal-submucosal somatostatin-containing cells in inflammatory bowel diseases (IBD), the total numbers of somatostatin-containing endocrine cells (SCEC) and submucosal ganglion cells (SGC) were counted in Crohn's disease (CD) and ulcerative colitis (UC). Tissue specimens from 25 CD and 25 UC patients were fixed in Hollande's fixative immediately after resection and were investigated by immunohistochemical staining. A single specimen was collected from 25 colorectal cancer patients, the control group. There was a significant difference in the number of SCEC between the tissues taken from the proximal colon (ascending and transverse colon) and the distal colon (descending and sigmoid colon). The distal colon tended to contain more somatostatin-immunoreactive cells than did the proximal colon. In IBD, SCEC were decreased in number compared with the controls. This decrease was related to the degree of inflammation in CD; the higher the grade of inflammation, the lower the number of SCEC. The number of SGC was decreased in IBD: however, a significant decrease was noticed only in CD. The anatomic origin and the degree of inflammation did not affect the number of SGC. In the present study, the decrease of somatostatin-containing cells was noticed in both CD and UC, but there was no significant difference between CD and UC. Therefore, it was assumed that this decrease was secondary to inflammation. However, the decrease of somatostatin, which works as an inhibitory peptide for inflammation, might have some role in the pathogenesis of IBD.