Twenty-five Bifidobacterium strains isolated from infant feces were identified by sugar fermentation patterns and whole-cell protein analysis. Using gradient SDS-PAGE, six characteristic protein bands of the genus were detected in 40 strains of bifidobacteria but not in lactobacilli. Computerized numerical analysis enabled strains to be grouped in two main clusters. Strains of Bifidobacterium bifidum belong to a well-differentiated cluster that joins the cluster of the remaining species at 0.582 similarity. The predominant species among isolated strains from infant feces were B. bifidum, B. longum, and B. breve. Probiotic and technological indicators such as surface properties, inhibitory capacity, resistance to bile and low pH, and ability to grow under aerobic conditions were studied. Not all desirable characteristics were present in a single strain. In general, adherent and inhibitory strains were not resistant to bile, low pH, and aerobic conditions. Only 10 of 40 strains were resistant to 0.5% bile.Centro de Investigación y Desarrollo en Criotecnología de Alimentos