A fractionated pancreatic antigen was prepared using a monoclonal antibody, SP3-1, which reacts with the duct cells of various exocrine organs, The cell-mediated immune response to this antigen was studied by the leukocyte migration inhibition test (LMT) in patients with chronic pancreatitis (CP), Sjögren’s syndrome (SjS), and chronic sialoadenitis (CSA). The migration index (MI) for the LMT was 0.97 ± 0.07 in normal controls (mean ± SD, n = 11, range: 0.88-1.08). A positive LMT result (MI < 0.82 = mean -2SD in controls) was obtained in 7/8 (88%) SjS patients, 4/22 (18%) CP patients, 2/3 CP patients with SjS, and 0/3 CSA patients. These results indicated sensitazation against the pancreatic antigen in most SjS patients and some CP patients, and may suggest that an immune response to a common antigenic determinant of the duct cells of exocrine glands plays a role in the pathophysiology of both diseases.