The fecal flora of nine bottle-fed infants with biliary atresia were examined to determine the effects of the absence of bile on the intestinal flora. The numbers of the following fecal flora were significantly reduced compared with healthy infants: bifidobacteria, lecithinase-negative clostridia, streptococci, and staphylococci. Bifidobacteria were reduced to the greatest extent, constituting 75% of total flora in healthy comparison infants but only 2.4% in infants with biliary atresia. The most prevalent bacteria in infants with biliary atresia were enterobacteria.