Fecal microflora of 12 breast-fed(BF) and 15 formula-fed(FF) infants were investigated at 1 year after birth and the results were compared to those that had previously been obtained from the same subjects at 1 week after birth, and before and after weaning. At 1 year the two lactation groups showed no significant differences both in frequencies and numbers of each major bacterical species, except eubacteria, which showed higher frequency in FF infants. Bifidobacteria appeared as dominant species in 50% BF infants, heres bacteroides in 73.3% FF infants. Fecal pH was lower, though insignificant, in BF infants(6.5$pm$0.4) than in FF infants(6.8$pm$0.5). In BF infants, the number of bifidobacteria, clostridia, and E. coli deceased from birth up to 1 year, whereas the number of bacteroides similar trends to BF infants except that the number of bifidobacteria increased, but insignificantly. This research showed that the floral differences resulted not from the age, but from the types of feeding and that breast feeding and that breast feeding could be better than formula feeding in the BF infants had more stable floral composition and bowels with lower pH, which can play a protection role against pathogen infection.