20 patients participated in this study, who had undergone comprehensive periodontal treatment at the Department of Operative Dentistry and Periodontology at Heidelberg University Dental School from 1998 to 2000 and who exhibited probing pocket depths (PPD) = 5 mm and BOP or >/= 6 mm at single rooted teeth. Two different treatments were assigned randomly: DOXI (exclusively subgingival application of a 14% doxycyclin gel) or SRP (mechanical subgingival debridement using sonic scalers). Clinical examinations (PlI, PPD, RAL-V, GI) were obtained before, 3, and 6 month after therapy. In 20 patients (8 female) from 30 to 76 years of age a total of 103 single rooted teeth (DOXI: 61; SRP: 42) were treated. In both groups statistically significant (p /= 7 mm) than in shallow pockets (PPD 5-6 mm). For therapy of residual or recurrent pockets during supportive maintenance care subgingival application of the 14% doxycyclin gel provides as good clinical results as subgingival debridement with sonic scalers. Schlagwörter: lokale Antibiotikaapplikation, Doxicyclin, unterstützende Parodontitistherapie, Schallinstrumentierung