The aim of the study was to investigate the potential role of nitric oxide (NO) on the microcirculation in experimental acute pancreatitis in rats. Twenty-five rats were divided into the following groups: group A (5 rats) = control; group B (5 rats) = acute pancreatitis induced by retrograde taurocholate infusion into the pancreatobiliary duct without treatment; group C (5 rats) = acute pancreatitis treated with the NO donor L -arginine; group D (5 rats) = acute pancreatitis treated with the NO synthase inhibitor N-nitro- L -arginine (L-NNA); group E (5 rats) = without pancreatitis receiving L -NNA. The animals were observed throughout 4 h. The microcirculatory values of the pancreas, liver, colon, stomach and kidney were measured by means of laser Doppler flowmetry. Three animals of group D died after the third hour of the experiment. In rats with pancreatitis, a rapid decrease in microcirculatory values was observed. The most pronounced drop in capillary blood flow within all the organs was observed in rats treated with the NO synthase inhibitor L -NNA, L -arginine administration in rats with acute pancreatitis slightly improved the microcirculatory values, although the improvement was significant in colon perfusion only. We conclude that NO may have a beneficial influence on the capillary organ perfusion in acute pancreatitis. The administration of an NO synthase inhibitor seems to have a detrimental effect on acute pancreatitis.