ABSTRACT.Rectal cultures from Swedish and Pakistani hospital‐delivered newborn infants were analysed regarding the early aquisition of enterobacteria. Swedish infants were delivered vaginally, Pakistani infants were delivered either vaginally or by caesarean section. The Swedish infants were all breast‐fed, whereas breastfeeding was incomplete and often started late among the Pakistani infants. Both groups of Pakistani infants were more rapidly colonized with enterobacteria than were the Swedish infants. Cultures from Swedish infants seldom yielded more than one kind of enterobacteria;E. coliandKlebsieflawere most frequently isolated.E. colidominated in both Pakistani groups, but especially caesarean section delivered infants were in addition often colonized withProteus, Klebsiella, EnterobacterorCitrobacterspecies. Breastfeeding from the first day of life reduced colonization withKlebsiella/Enterobacter/Citrobucter.The results suggest that environmental exposure, delivery mode and early feeding habits all influence the early intestinal colonization with enterobacte