Twenty-six Bifidobacterium strains were isolated from human faeces. Seven strains were identified as B. bifidum, 4 strains as B. breve, 10 strains as B. longum, 2 strains as B. pseudocatenulatum and 3 strains as B. dentium by 16S rDNA analysis. The isolates from human origin showed strong adherence to the human tissue cultures. Three out of the 12 tested isolates repressed the growth of enteropathogenic bacteria. Utilisation of 9 commercially available oligosaccharides was tested by both Bifidobacteria and enteropathogens. Pro-, pre- and synbiotic food was made. Their effect was evaluated in in vivo feeding experiments, where healthy and antibiotic treated mice were used as test animals. During the four-week feeding period the composition of the colonic microbiota of the healthy mice did not change characteristically in any feeding group. However, the microbiota of mice in which it had been killed by antibiotic treatment was recovered by feeding with synbiotic food.