The acquisition of the human oral bacterial flora follows a relatively well known sequence of succession that can be influenced by various host factors. These factors have not been studied in the mouse. In the present work, we followed the bacterial colonization of the oral cavity of mice from birth, and tested our mouse model for its suitability in studying the influence of weaning and puberty on the indigenous oral bacterial flora. We observed that the first colonizers were staphylococci, followed by lactobacilli. The proportions of these two predominant bacteria fluctuated for a period of 30-50 days, but evolved towards the proportions previously observed among the indigenous bacterial species of 6-8 week-old BALB/c male mice (predominantly Lactobacillus murinus and Staphylococcus aureus). The weaning period significantly altered the equilibrium among the oral bacterial flora. This equilibrium was not significantly modified during puberty.