We present a review of the microvascular morphology of the pancreas and microstructure of the pancreatic lobule, and introduce our experimental results on pancreatic microcirculation following acute pancreatitis. Impairment of pancreatic microcirculation in the early phase of acute pancreatitis may play a key role in the progression of this disease. Possible contributory mechanisms include increased vascular permeability, reduced blood flow, leukocyte-endothelial cell interaction, and intravascular thrombus formation. We achieved direct-visualization and quantification of changes in microvascular permeability and leukocyte behavior in the pancreas with acute pancreatitis using an in vivo microscope system and off-line computer analysis. Bradykinin and oxygen radicals have been demonstrated to be involved in the increased vascular permeability in the early stage of cerulein pancreatitis. Gabexate mesilate (FOY) prevents the increase in vascular permeability, resulting in a decreased number of rolling leukocytes. Leukocyte adherence to the pancreatic microcirculation is a secondary event following permeability changes in acute pancreatitis. Leukocyte infiltration during aggravation of acute pancreatitis is mediated by leukocyte-endothelial cell interaction via leukocyte integrin CD11b/18. The diamino-pyridine derivative IS-741 inhibits the progression of pancreatic inflammation by down-regulating the expression of CD11b/18.