Biliary stent blockage and microbial colonization is a common complication associated with polyurethane stents used for the relief of bile-duct obstruction caused by benign or malignant disease. In an attempt to overcome this problem the application of a 'Teflon' (polytetrafluoroethylene) stent and an antimicrobial benzalkonium chloride (BZC) impregnated polymer were investigated. The effects of these materials on microbial colonization were compared to a polyurethane stent in vitro in broth or bile. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of BZC for three commonly isolated biliary stent pathogens, Staphylococcus epidermidis, Enterococcus faecium and Enterobacter cloacae were also determined. All the isolates were sensitive to BZC. The growth kinetics of the three organisms in broth and in human pooled bile were similar. Adherence to the BZC impregnated polymer was significantly reduced as compared to the polyurethane and Teflon stents (P < 0.05) in nutrient broth. In bile, fewer organisms attached to the Teflon as compared with the polyurethane stent (P < 0.05) for all organisms. For two of the three test organisms there was less bacterial adherence to the Teflon than to the BZC impregnated polymer. The Teflon and antimicrobial stent materials studied may prevent biliary stent blockage resulting from microbial colonization.