Objective: Report of clinical and microbiological periodontal findings before and six months after treatment of two siblings with Papillon-Lefèvre syndrome (PLS). Methods: Two brothers, RG 3 and NG 5 years of age, were referred for treatment due to premature mobility of their deciduous teeth. Probing depths (PPD), attachment levels (PAL-V), and furcation involvements were examined clinically. Panoramic radiographs were taken. Subgingival plaque samples within the deepest pocket of each tooth were taken and analyzed by real-time PCR for Actinobacillus actinomycetemcomitans (AA), Porphyromonas gingivalis, Tannerella forsythensis, Treponema denticola, Fusobacterium nucleatum, and Prevotella intermedia. One-stage full-mouth scaling and extraction of hopeless teeth were performed under general anesthesia, followed by systemic amoxicillin and metronidazole for seven days. Clinical and microbiological analyses were performed six months after treatment. Results: Before treatment, both siblings had exhibited PPD of up to 13 mm, Class III furcation defects at four teeth, and marginal suppuration. AA was detected in both patients and at all teeth at levels ranging from 3.0 × 102 to 5.1 × 106. Both patients exhibited palmar and plantar hyperkeratosis. Seven teeth were extracted from RG, nine from NG. Six months after treatment, PPD had been reduced to £ 5 mm. AA was not detected in any of the remaining teeth. Conclusion: Even periodontally affected deciduous teeth of PLS patients can be treated successfully. Suppression of AA to below detection level seems to be of high significance. Schlagwörter: Papillon-Lefèvre-Syndrom