This study evaluated the 6-month clinical response to sustained-release tetracycline fibers used alone or with scaling and root planing in 25 adult periodontal maintenance patients. All subjects had at least one pocket >= 4.0 mm that bled on probing and required therapy. Tirty-six teeth were treated with tetracycline fibers for 7 to 12 days; twelve of the 36 teeth also received scaling and root planing. The selection of teeth for scaling and root planing was based on the condition of the teeth. Therapeutic results were evaluated by changes in probing depth and frequency of bleeding on probing. Use of tetracycline fibers and fibers with scaling produced 1.8- and 1.7-mm reductions in probing depth, respectively, 1 month after treatment; reductions declined to 1.3 and 0.8 mm at 3 months, but rebounded to 1.5 and 1.3 mm at 6 months. The percentage of teeth exhibiting bleeding on probing decreased from 100% at baseline to 68% and 50% in the fiber and fiber plus scaling groups, respectively, at 6 months. None of the diffeerences was statistically significant. Tetracycline fibers clearly decreased clinical signs of periodontal inflammation. Addition of scaling and root planing at the time of fiber placement furtehr decreased, although not significantly, the degree of inflammation.