Résumé : PMN leukocytes from circulating blood, were investigated using the following parameters: chemiluminescence, superoxide generation, exocytic degranulation, lactoferrin, myeloperoxydase and protein-kinase-C activities. The results did not allow to point out any significative discrepancy between samples collected from either patients suffering of periodontal disease or healthy individuals. However, the phagocytic ability (as measured by light emission and superoxide production) was found to be severely inhibited in both instances, when PMN leukocytes were incubated in the presence of succinic acid. Similarly, protein-kinase-C activity in these cells, collapsed when the pH was brought down to 5.5. These data and the available literature indicate that pH decrease as well as succinic acid release in the crevicular fluid, may play a role in the pathogeny of chronic periodontitis in adults.