Periodontitis resulting from Papillon-Lefevre Syndrome has been known to cause early loss of primary dentition with subsequent involvement of the permanent dentition. In this stu dy, two Papillon-Lefevre Syndrome patients were followed for 3 years after initial treatment and improvement of their periodontal condition. In addition, two new cases of Papillon-Lefevre Syndrome are presented. The follow-up treatment of the first two patients included monitoring the oral hygiene and performing ultrasonic scaling. Their present clinical appearnace is very satisfactory. The periodontal condition of the third (new ) patient was brought under control by extracting the involved deciduous teeth under antibiotic coverage, and by scaling and root planing the already erupted permanent teeth as well as by maintaining a high standard of oral hygiene. In the fourth case, all permanent teeth had erupted and the periodontium had already been severely destroyed. Actinobacillus actinomycetemcomitans was not detected by microbiologic examination after the periodontal conditions improved, except in the fourth case. Western blot analysis showed that the three first three patients had positive antibody response to the same anti gens of Actinobacillus actinomycetemcomitans. Phagocytosis by polymorphonuclear neutrophil leukocytes) had not decreased, but the expression of surface receptors of polymorphonuclear neutrophil leukocytes was within the normal limits.