The aim of this study was to evaluate the oral health status in young swimmers, involving an assessment of salivary cariogenic bacteria, of S-IgA concentration, before and after training sessions. One hundred and eighteen swimmers and 48 sedentary individuals were selected. Before training sessions (T1), a clinical monitoring was performed and the following parameters were recorded: DMFT, Plaque Index (PlI), Gingival Index (GI). At T1 and after training sessions (T2), stimulated saliva was collected and subjected to microbiological and immunological analysis. The athletes trained 2 h x 5 days/week and showed a good state of oral health related to a low prevalence of parafunctional behavior, decay presence, lower GI values, compared to controls. The swimmers total bacterial count and the load of S. mutans, S. sanguis, L. fermentum and A. gerencseriae underwent a statistically significant increase at T2. S. mutans, S. mitis and L. acidophilus mean values were significantly higher in swimmers than in controls. Swimmers S-IgA average value decreased significantly at T2. Therefore, the single physical exertion is a period characterized by the most intensive intraoral growth of cariogenic bacteria and a time of less intensive salivary functions and physiologic response as a decrease in the level of S-IgA.