The purpose of this controlled case series was to assess the adjunctive efficacy of controlled topical tetracycline HCl application in the treatment of infection associated periimplant mucositis or mucosal hyperplasia. Eight patients with at least 2 endosseous implants showing clinical signs of periimplant mucosal hyperplasia or mucositis were enrolled. All implants received supra- and subgingival scaling, with half of the implants receiving adjunctive controlled local delivery of tetracycline HCl (test). Control implants did not receive any other therapy aside from scaling. Clinical parameters were assessed at baseline, 4, and 12 weeks. Scaling plus controlled local delivery of tetracycline HCl markedly reduced periimplant mucosal hyperplasia in 4 of 5 test implants and demonstrated a trend towards a reduction of bleeding on probing scores. Scaling alone had no effect on mucosal hyperplasia in the 2 control implants presenting with this condition nor bleeding on probing scores. In both groups, plaque index scores were slightly reduced at 4 weeks but returned to baseline values at 12 weeks, whereas pocket probing depths, clinical attachment levels, and probing bone levels remained unchanged during the course of the trial. The observed trends suggest that scaling plus controlled local delivery of tetracycline HCl may have beneficial effects. Randomized controlled trials employing a sample size high enough to reach sufficient statistical power are needed to definitively assess the efficacy of controlled local tetracycline HCl delivery on periimplant diseases.