To evaluate the influence of tetracycline gel, brushed on tooth surfaces, on periodontal clinical parameters following root debridement. 20 subjects diagnosed with chronic periodontitis and presenting a minimum of two proximal sites on anterior teeth (maxillary or mandibular) with probing depth +/- 5 mm, were selected. Following oral hygiene instructions and ultrasonic supragingival instrumentation, subjects were assigned to one of the following groups: RDS--root debridement with Gracey curettes and root brushing with saline solution; and RDT--root debridement with Gracey curettes and root brushing with 40% tetracycline gel. Full-thickness flaps were reflected and instrumentation was performed using a clinical microscope to optimize calculus detection. Probing depth (PD), relative gingival margin level (RGML) and relative attachment level (RAL) measures were registered at five visits: baseline and days 30, 60, 90 and 120 postoperative. Both approaches were able to markedly reduce the PD values from baseline in all periods (P < 0.0001). No differences were found for RAL values in any of the groups. No differences were found between groups. In conclusion, the application of tetracycline gel does not seem to provide any additional improvement on clinical periodontal parameters after root debridement.21168-70