Dietary inoculates for weaned pigs often include lacobacilli, but the effects of age and diet on the ecology of adherent lactobacilli are not well known. Four experimental treatments included 16 newborn piglets: a pre-weaning treatment (PW) included four pigs that were sacrificed at 28 days of age; a sow treatment (Sow) had four pigs that remained with the sow (Sow) from 28 to 38 days of age and were sacrificed at 38 days of age; and two treatments in which four pigs each, were placed on a corn-soy diet with (CSL), or without (CS) 40% lactose. Adherent lactobacilli were isolated from the pars esophagus, ileum, and cecum, and characterised phenotypically. A 23S rDNA probe hydrized toEcoRI orPstI digested DNA, and a 74.8% cut-off individualize isolates into 36 clusters. The most predominant strains found in the Sow, CSL, and CS treatments were the same, but different strains predominated in the PW animals. The most predominant strains found in the pars esophagus and ileum were the same, but different strains predominated in the cecum.