This study was designed to evaluate the effects of algal and yeast β-glucans on the porcine gastrointestinal microbiota, specifically the community ofLactobacillus, Bifidobacteriumand coliforms. A total of 48 pigs were fed four diets over a 28-day period to determine the effect that each had on these communities. The control diet consisted of wheat and soya bean meal. The remaining three diets contained wheat and soya bean meal supplemented with β-glucan at 250 g/tonne fromLaminaria digitata,Laminaria hyperboreaorSaccharomyces cerevisiae. Faecal samples were collected from animals before feeding each diet and after the feeding period. The animals were slaughtered the following day and samples were collected from the stomach, ileum, caecum, proximal colon and distal colon. Alterations inLactobacillusin the gastrointestinal tract (GIT) were analysed using denaturing gradient gel electrophoresis (DGGE) profiles generated by group-specific 16S rRNA gene PCR amplicons. Plate count analysis was also performed to quantify total coliforms. DGGE profiles indicated that all β-glucan diets provoked the emergence of a richer community ofLactobacillus. The richest community of lactobacilli emerged after feedingL. digitata(LD β-glucan). Plate count analysis revealed that theL. hyperborea(LH β-glucan) diet had a statistically significant effect on the coliform counts in the proximal colon in comparison with the control diet. β-glucan fromL. digitataandS. cerevisiaealso generally reduced coliforms but to a lesser extent. Nevertheless, the β-glucan diets did not significantly reduce levels ofLactobacillusorBifidobacterium.DGGE analysis of GIT samples indicated that the three β-glucan diets generally promoted the establishment of a more varied range ofLactobacillusspecies in the caecum, proximal and distal colon. The LH β-glucan had the most profound reducing effect on coliform counts when compared with the control diet and diets supplemented withL. digitataandS. cerevisiaeβ-glucans.