<i>Background/Aims:</i> It has been suggested that the distal portion of the dorsal pancreatic duct and the ventral pancreatic duct usually merge into the main pancreatic duct, and the proximal portion of the dorsal pancreatic duct becomes the accessory pancreatic duct. In this study, we investigated the embryology of the accessory pancreatic duct roentgenographically and immunohistochemically. <i>Methods/Results:</i> The accessory pancreatic duct shows two different patterns in pancreatograms: the long and the short type. The accessory pancreatic duct of the long type forms a straight line and joins the main pancreatic duct at the neck portion of the pancreas. The accessory pancreatic duct of the short type joins the main pancreatic duct near its first inferior branch. Long inferior branches from the accessory pancreatic duct were found in 74.6% with the long type, significantly more often than in the short type (29.3%). Patency of the long type was (74.5%) significantly greater than in the short type (36.2%). Immunohistochemically, we found the main pancreatic duct between the junction with the accessory pancreatic duct and the neck portion of the autopsy pancreas in the short type was located within the ventral pancreas, characterized by pancreatic polypeptide-rich islets. <i>Conclusion:</i> The long type represents a continuation of the main duct of the dorsal primordium. The short type is very likely formed by the proximal main duct of the dorsal primordium and its long inferior branch, with the main duct of the dorsal primordium at the point of connection with the main duct of the ventral primordium being obliterated and replaced by this additional communication.