A new very thin glass fiber endoscope ("baby scope") has been developed, which can be passed through the channel of a modified duodenoscope ("mother scope") for catheterization of the choledochus or of the pancreatic duct. Peroral choledocho-pancreatoscopy (PCPS) was performed in 9 patients, the endoscopic results are presented. Other new auxiliary instruments for diagnostic or therapeutic purposes in biliary or pancreatic diseases are described: a brushing catheter, a special biopsy forceps, a retention probe and a balloon-tipped catheter.