The pancreatic lesions in 6- to 36-week-oldspontaneously hypertensive rats (SHR), stroke prone SHR (SHRSP) and Wistar-Kyoto rats (WKY) were examined histopathologically. Inflammatory cell infiltration with hemorrhage and stromal fibrosis became evident in 12-week-old SHR and SHRSP together with acinar atrophy and/or degeneration and ductular proliferation. These changes in SHR and SHRSP were even more prominent at the age of 24 weeks and extremely severe at 36 weeks. In addition, in SHR and SHRSP over 12 weeks of age, small necrosis of acinar cells was found occasionally together with fibrosis and arteriosclerosis. Pancreatic arteriosclerosis was marked in SHR and SHRSP over 24 weeks of age at the level of arterioles <200 p,m in diameter. Adrenergic nerve fibers stained by fluorescence his-tochemistry were present around the pancreatic arteries and ducts and within the parenchyma, and they were denser in SHR and SHRSP than in WKY, indicating hy-perinnervation of the sympathetic nervous system in SHR and SHRSP. It is suggested that the pancreatic ischemia caused by arteriosclerosis due to facilitation of the sympathetic nervous system is an important factor in the pathogenesis of the spontaneous pancreatitis of SHR and SHRSP.