The influence of fructooligosaccharides (FOS) and their monomeric components on bile salt resistance of Bifidobacterium breve ATCC 15700, Bif. longum ATCC 15707 and Bif. animalis ATCC 25527 was examined. The neosugars induced fructofuranosidase activities for the degradation of these saccharides. For the three strains tested the growth was identical and bile salts had the same inhibitory effect on growth whatever the carbohydrate used. The survival of Bif. breve and Bif. longum, in the presence of glycodeoxycholic acid depended, however, on carbohydrates: the toxic effects of the bile salt could be partly alleviated by the addition of a metabolizable C-source. For Bif. animalis, the presence of any carbohydrate in the incubation medium did not enhance the viability of the strain. But in the three deconjugating strains of bifidobacteria studied, the presence of neosugar during the growth led to improved resistance to the bactericidal effect of the bile salt compared with the monomeric components of these neosugars (glucose and fructose).