Microflora in 14 breast-fed(BF) and 15 formula-fed(FF) infants were investigated before (2-3 months after birth) and after weaning (5-7 months birth) to find the floral differences between the two lactation groups and the floral changes after weaning. Bifidolbacteria showed the highest count among the species of microflora in the BF group before and after weaning, but in the FF group, streptococci showed the highest count before weaning and bifidobacteria after weaning. Before weaning , the count of bifidobacteria, lactobacilli and total acaerobes were significantly higher in the BF group than in the FF. However, the frequencies of clostridia and klesidella , along with the counts of streptococci and eubacteria, were higher in the FF group. After weaning , the only difference was that the total count of aerobic bacteria was higher in the BF group. The counts of streptococci in the BF group and lactobacilli and total anaerobes in the FF group after weaning were significantly higher than before weaning. However, the count of total aerobes in the FF group after weaning was significantly lower than the count before weaning.