Camostat mesilate, an orally available proteinase inhibitor, is clinically used for treatment of pancreatitis. Given recent evidence that pancreatic proteinases including trypsin and/or proteinase-activated receptor-2 (PAR2) might be involved in pancreatic pain, we examined if camostat mesilate could suppress spinal Fos expression, a marker for neuronal activation, following specific application of trypsin to the pancreas, and pancreatitis-related referred allodynia. Trypsin, administered into the pancreatic duct, caused delayed expression of Fos proteins in the superficial layer of the bilateral T8 and T9 spinal dorsal horns in rats. The trypsin-induced spinal Fos expression was completely abolished by oral pre-administration of camostat mesilate at 300 mg/kg. After hourly repeated (6 times in total) administration of caerulein, mice showed typical symptoms of pancreatitis, accompanied by mechanical allodynia in the upper abdomen (i.e., referred hyperalgesia/allodynia), as assessed by use of von Frey filaments. Camostat mesilate at 100-300 mg/kg, given orally twice before the 1st and 4th doses of caerulein, abolished the pancreatitis-related abdominal allodynia, while it partially prevented the inflammatory signs. The same doses of camostat mesilate, when administered once after the final dose of caerulein, also revealed significant anti-allodynic effect. These data suggest that camostat mesilate prevents and/or depresses pancreatitis-induced pain and/or referred hyperalgesia/allodynia, in which proteinases including trypsin would play a critical role.