In order to investigate the distribution of dominant Bifidobacterium species in intestinal microflora of Korean adults and seniors, SDS-PAGE profiles of whole cell proteins were used for the identification of bifidobacteria. To confirm the reliability of SDS-PAGE, the Bifidobacterium species identified by SDS-PAGE of whole cell proteins were validated by using 16S rDNA sequencing analysis. The results of SDS­PAGE corresponded well with those determined by the analysis of 16S rDNA sequencing. Based on the analysis of SDS-PAGE patterns on unidentified fecal strains which showed positive in fructose-6-phosphate phosphoketolase activity, B. adolescentis, B. longum, and B. bifidum were identified in the feces of adults, and B. adolescentis, B. longum, B. bifidum, B. breve, and B. dentium were identified in those of seniors. In most of the fecal samples tested, the predominant Bifidobacterium species consisted of only a few species, and differences in the distribution and numbers of Bifidobacterium species were observed between adults and seniors. B. adolescentis and B. longum were found to be the most common species in feces of adults, but not in seniors. Accordingly, the distribution and abundance of bifidobacteria in the human intestinal microflora varied depending on the age of hosts.