Serum C reactive protein was determined in 30 control subjects, 32 patients with pancreatic cancer, 28 with chronic pancreatitis and 23 with extra-pancreatic diseases of the upper gastrointestinal tract. The aim was to ascertain possible alterations of this index in chronic pancreatic disease and to speculate on some influencing factors. Higher C reactive protein levels were found in pancreatic cancer as compared to controls. Pancreatic cancer patients with systemic metastases had higher levels of this index compared to those with non-metastatic disease. Raised concentrations of C reactive protein were detected in 7/28 subjects with chronic pancreatitis. In this group these higher levels were found in patients in a relapsing phase of the disease; no association was observed with pancreatic pseudocysts. Among all subjects a correlation was found, between C reactive protein and age; patients with abnormal fasting blood glucose levels or increased white blood cell count had higher levels of this protein as compared to the remaining patients. We may conclude that C reactive protein increases in pancreatic cancer, specially in relation to tumour extent; in chronic pancreatitis it reflects the inflammatory status of the gland. While acting in the context of the acute phase response, this test may provide an adjunct in evaluating patients with a chronic pancreatic disease.