The effects of chronic administration of methamphetamine on pancreatic tissues were histopathologically studied in experimental models. Methampheta e (1ml/kg body weight/day) was subcutaneously injected into 14 five-week-old male Wistar Kyoto rats (WKY) for 12 weeks. Age and sex matched 5 WKY rats served as controls. With light microscopy, some scattered edematous lesions and moderate vacuolization were demonstrated in the pancreas of 8 of the methamphetamine treated rats. However, in 4 of the rats, severe regional hemorrhage, partial acinal cell necrosis, destruction of the acinall cells, neutrophile infiltration, interstitial vessel dilatation, interstitial edema and fatty cell invasion were observed after the injections of methamphetamine. In 2 other animals, fibrosis and cirrhosis-like lesions with destruction and degeneration of the acinal cells were observed the small vessels had a slight degeneration of the endothelial cells. In the control animals, no lesions, except for some edematous lesions were found. In all cases, there were no nesidioblastoss-like lesions or necrosis of the Langerhans's islets. In the immunohistochemical study using anti-α1-chymotrypsin antibody, more positive reactive cells were demonstrated among the interstitial and inter acinal cells, both in number and degree, in the methamphetamine treated rats. In addition to the animal model, there were 4 autopsy cases of sudden death in chronic methamphetamine abusers. The autopsies demonstrated a severe acute necrotic hemorrhagic pancreatitis, with only scattered slight hemorrhaging in the brain and lungs. These findings indicate that chronic administration of methamphetamine to rats evoked significant changes in pancreatic tissues including some degeneration of the endothelial cells of the small vessels in this hypoxia-vulnerable organ.