Intraductal papillary neoplasms of the bile ducts are increasingly being recognized as a distinct tumor type in the biliary tract as the counterpart of pancreatic intraductal papillary mucinous neoplasms. They are seen more in elderly population and can occur anywhere in the bile duct system including intra- and extra-hepatic. They are papillary or polypoid lesions that originate from and grow along the bile duct mucosa, and as such they have previously been classified as “papillary cholangiocarcinoma”, “papillomatosis” or “mucosal-growing(intraductal) cholangicarcinomas”. They are fundamentally “adenoma-carcinoma sequence”, and as such show many similarities to other tumoral intraepithelial neoplasms of the pancreatobiliary tract, namely intraductal papillary mucinous neoplasms (of pancreas), intra-ampullary papillary tubular neoplasms (ampulla), and, intracholecystic papillary tubular neoplasms (gallbladder). IPNB-associated invasive carcinomas are now recognized as a distinct subset among invasive biliary cancers in the College of American College of Pathologists’ synoptic reporting. Similar to their kindreds in the pancreatobiliary tract, IPNBs show a spectrum of neoplastic change from low-grade to high grade. The vast majority of cases, however, are associated with high-grade dysplasia, and, a significant proportion (~75%), also with invasive carcinoma. IPNBs may exhibit papillary, tubular or tubulopapillary growth patterns in variable amounts. Although they can be very large, invasive component can be small (smaller than 1 cm). However, unfortunately, they often get classified indiscriminately as “papillary cholangiocarcinoma” although their biology and behavior is substantially different than other subsets of biliary carcinomas. It can be challenging to distinguish invasive carcinoma from pagetoid extension of the intra-epithelial component into the accessory biliary glands. The size of invasive carcinoma ought to be reported separately, and T-staging of the tumor is to be based on the invasive component. Similar to IPMNs of the pancreas, IPNBs can exhibit different cell lineages. Some resemble colonic villous adenomas and exhibit intestinal differentiation markers such as CDX2 and MUC2. Similar to IPMNs, these intestinal type IPNBs can lead to colloid type invasive carcinoma which has a very protracted clinical course. Some IPNBs have gastric foveolar or pyloric patterns and also show MUC5AC or MUC6 expression. Many of them, however, have a non-descript biliary phenotype (also called “pancreatobiliary” subtype). Tumors with oncocytic cytology and exuberant papillary configuration are proving to be highly distinctive not only by morphology but also at molecular level. More importantly, this oncocytic type has highly peculiar clinical behavior, because, despite being very large, complex, and even necrotic, they are in fact often curable by resection, seldom showing dissemination or leading to mortality. Thus, increasingly the name of IOPN (intraductal oncocytic papillary neoplasm) is being preferred for these, to distinguish them from other IPNBs. In the meantime, there is another form of tumoral intraepithelial neoplasm being recognized in the biliary tract, under the name of intraductal tubulopapillary neoplasm (ITPN). These are highly similar to IPNBs by their clinical presentation, although they can form more solid nodular tumors both radiologically and grossly, and thus their “intraductal” nature may not be as readily evident. They are characterized microscopically by tubular configuration and lack of overt mucin production (defined just like their pancreatic counterparts). Despite their complexity and infiltrative appearance, they actually are curable tumors and have a long protracted clinical course. In conclusion, IPNB shows many analogies to intraductal neoplasia of the pancreatobiliary tract and intra-cholecystic tumors but at the same time it forms a pathologically and biologically distinct entity among biliary cancers.