The aim of this work was to examine by culturing the changes in the total and indicator populations of the feces of two individuals over 1 year and to identify the dominant microbial components of a single sample of feces from each donor. Populations and dominant bacteria from a sample of colonic mucosa from a further individual were also assessed. The culture results were then compared to those obtained with the same samples by 16S rDNA cloning and sequencing. High interindividual variation in representative microbial populations of the gastrointestinal tract (GIT) was revealed by both the culture and the culture-independent techniques. Species belonging to Clostridium clusters (XIVa, IV, and XVIII) predominated in both the fecal and the mucosal samples (except in the mucose cultured isolates), members of Clostridium coccoides cluster XIVa being the most numerous microorganisms. Species of gamma-proteobacteria (Escherichia coli and Shigella spp.), bifidobacteria, and actinobacteria appeared in lower numbers than those of clostridia. From the mucosal cultured sample, only facultative anaerobes and bifidobacteria were recovered, suggesting destruction of the anaerobe population during processing. In accordance with this, the microbial diversity revealed by 16S rDNA sequence analysis was greater than that revealed by culturing. Despite large interindividual differences, distinct human communities may have group-associated GIT microbiota characteristics, such as the low number of Bacteroides seen in the subjects in this study.