BACKGROUND The neural adhesion molecule N-CAM, a membrane bound glycoprotein, seems to play an important role in the development of normal tissue architecture and in contact-dependent inhibition of cell growth. METHODS We evaluated the behaviour of circulating N-CAM in patients with pancreatic cancer (24 cases) and chronic pancreatitis (15 cases) and compared it with that of 20 controls, 6 patients with colon adenoma, 31 with colorectal cancer or 21 with gastric cancer and ascertained the influence of tumor stage and grade on the findings. RESULTS N-CAM levels were significantly lower in patients with pancreatic cancer and chronic pancreatitis than in the other groups studied. High levels were found only in few colorectal carcinoma patients (4/31). No correlation was found between tumor stage and N-CAM levels when pancreatic and colorectal cancer were considered. However, low N-CAM levels were found in 50% of advanced, but not in early gastric cancer. When pancreatic, colorectal and gastric cancer were considered, poorly differentiated (G3) had lower levels of N-CAM than well (G1) or moderately (G2) differentiated tumors. The variations found in circulating N-CAM were comparable to those in CEA but not to those in CA 19-9. CONCLUSIONS a) perhaps because of its higher aggressiveness, pancreatic cancer is associated with low serum N-CAM levels unlike other gastrointestinal neoplasias; b) the association between aggressiveness and reduced N-CAM levels is borne out by the correlation found with the grade of differentiation; c) the reduced levels found in chronic pancreatitis suggest that this molecule plays a role in stromaparenchymal interactions, which might be altered in the presence of fibrotic phenomena.