The study investigates the composition, variability, and temporal stability of the intestinal microbiota in elderly individuals. Using pyrosequencing of 16S rRNA gene V4 region amplicons, the researchers characterized the fecal microbiota of 161 subjects aged 65 years and older, along with 9 younger control subjects. The results show that each individual had a unique microbial profile, with a dominant phylum of *Bacteroidetes* (57%) and a secondary phylum of *Firmicutes* (40%). The elderly microbiota was distinct from that of younger adults, characterized by a higher proportion of *Bacteroidetes* and different abundance patterns of *Clostridium* groups. The core microbiota of elderly subjects was also different from that of younger adults, with a higher abundance of *Faecalibacterium* spp. and *Clostridium* cluster IV. The study found that the fecal microbiota of the elderly showed temporal stability in most subjects, with 85% of subjects having microbiota compositions similar to their baseline samples at 3 months. However, the elderly microbiota exhibited significant interindividual variability, with dramatic differences in the proportions of various phyla and genera. The findings highlight the unique and dynamic nature of the gut microbiota in the elderly, which may have implications for health and disease.The study investigates the composition, variability, and temporal stability of the intestinal microbiota in elderly individuals. Using pyrosequencing of 16S rRNA gene V4 region amplicons, the researchers characterized the fecal microbiota of 161 subjects aged 65 years and older, along with 9 younger control subjects. The results show that each individual had a unique microbial profile, with a dominant phylum of *Bacteroidetes* (57%) and a secondary phylum of *Firmicutes* (40%). The elderly microbiota was distinct from that of younger adults, characterized by a higher proportion of *Bacteroidetes* and different abundance patterns of *Clostridium* groups. The core microbiota of elderly subjects was also different from that of younger adults, with a higher abundance of *Faecalibacterium* spp. and *Clostridium* cluster IV. The study found that the fecal microbiota of the elderly showed temporal stability in most subjects, with 85% of subjects having microbiota compositions similar to their baseline samples at 3 months. However, the elderly microbiota exhibited significant interindividual variability, with dramatic differences in the proportions of various phyla and genera. The findings highlight the unique and dynamic nature of the gut microbiota in the elderly, which may have implications for health and disease.