The differentiation of infantile biliary malformations from primary parenchymal diseases is difficult. The recent development of a pediatric side-viewing endoscope (PJF Endoscope; Olympus Corporation of America) provided an opportunity to investigate the usefulness of endoscopic retrograde cholangiography (ERC) for precise visualization of the extrahepatic biliary passages in infants with persistent cryptogenic cholestasis. ERC was performed in 12 patients, with visualization of the existing extrahepatic bile ducts in 4. The entire biliary system was visualized in one, excluding extrahepatic biliary atresia and choledochal cyst. The reduced caliber of the intrahepatic bile ducts and histological observations in a percutaneous liver biopsy supported the diagnosis of intrahepatic biliary hypoplasia in this case. An intact hepatic portochole cystostomy was documented in one, although the intrahepatic biliary system was not delineated. Atresia of the hepatic bile ducts proximal to the gallbladder was documented in two. Of the eight patients in whom extrahepatic bile ducts were not visualized by ERC, six had extrahepatic biliary atresia confirmed at exploratory laparotomy. The papilla of Vater could not be located in four of these six infants. The remaining two had neonatal hepatitis. ERC may offer a useful alternative to operative cholangiography in selected infants with persistent cholestasis and acholic stools.