This study provides a comprehensive survey of the spatial and temporal bacterial composition of biliary stent biofilms. The bacterial diversity, distribution and dynamics of 59 biliary and 4 pancreatic stent communities from 40 patients being treated at two different hospitals, which implant stents either simultaneously or consecutively, were characterized by single-strand conformation polymorphism (SSCP) analysis. Fifty-one phylotypes belonging to 5 bacterial phyla and 24 bacterial families were detected across 63 stents. This is a much broader diversity than previously detected through culture-dependent methods, particularly in regard to the diversity of obligate anaerobes. Stent bacterial diversity was patient-dependent and more similar when stents were implanted simultaneously rather than consecutively. Stent bacterial community composition differed between hospitals specifically because of the difference in abundance of Bifidobacteria. Co-colonization of Veillonella sp., Streptococcus anginosus and organisms closely related to Fusobacterium nucleatum revealed a potentially important attachment and survival strategy that has yet to be reported in biliary stents. This work reveals a more complete survey of the identities of bacterial species that form biofilms in biliary stents, their co-colonization patterns and the natural variation in species composition between different patients, hospitals and locations along the stent. Consideration of the community composition from individual patients will allow tailoring of prophylactic antibiotic treatments and thus will make the management of stent biofilms more effective.