Regional distribution and relative frequency of endocrine cells in the pancreas of the red-eared slider, Trachemys scripta elegans, were investigated by immunohistochemical methods. Chromogranin (Cg) A-, serotonin-, insulin-, glucagon-, somatostatin-, bovine pancreatic polypeptide (BPP)- and human pancreatic polypeptede (HPP)-immunoreactive cells were identified in this study. Most of immunoreactive cells in the exocrine and endocrine pancreas (Langerhans islet) were generally spherical or spindle-shaped (open-typed cell), while occasionally cells round in shape (close-typed cell) were found in the basal portion or interepithelial regions of the pancreatic duct. These immunoreactive cells were located in the exocrine, endocrine pancreas and/or basal or interepithelial portion of the pancreatic duct. Serotonin-immunoreactive cells were found in the basal portion of epithelia of the pancreatic duct at a low frequency and interacinar region of the exocrine at a moderate frequency. Insulin-immunoreactive cells were found in the central portion of the endocrine pancreas, interacinar regions of the exocrine pancreas and basal portion of the epithelia of the pancreatic duct at high, moderate and low frequencies, respectively. Glucagon-immunoreactive cells were detected in the periphery of the endocrine pancreas, interacinar region of the exocrine pancreas and basal portion of the epithelia or interepithelia of the pancreatic duct at high, moderate and moderate frequencies, respectively. Somatostatin-immunoreactive cells were dispersed in the whole area of the endocrine pancreas, interacinar regions of exocrine pancreas and basal portion of the epithelia or interepithelia of the pancreatic duct at a moderate frequency. BPP- and HPP-immunoreactive cells were detected in the iinteracinar region of the exocrine pancreas at moderate and hige frequencies, respectively. However, no Cg A- and motilin-immunoreactive cells were detected in this study.