Considerable problems have been reported in the eradication of Actinobacillus actinomycetemcomitans from periodontal sites. The present communication describes the 2-year results of a comprehensive combined mechanical/surgical and adjunctive minocycline (200 mg/day for 3 and another 2 weeks) treatment regimen in 28 patients with A. actinomycetemcomitans-associated periodontitis. Elimination of A. actinomycetemcomitans at periodontal sites was a prerequisite for gain of clinical attachment of > or = 2 mm or decrease of probing depth to < or = 4 mm after subgingival scaling plus minocycline (p < 0.01). Whereas 2 years after active treatment A. actinomycetemcomitans could not be detected at monitored sites in 23 patients, the organism was found on buccal mucosa and in saliva in 17 and 12 cases, respectively. One or 2 years after periodontal surgery, there was a significant association between log10-numbers of A. actinomycetemcomitans in buccal samples and numbers of residual pockets of > or = 7 mm as well as gingival sites with overt gingivitis (R2 = 0.687, p < 0.001). Present results indicate failure of an even prolonged administration of adjunctive minocycline to eliminate oral A. actinomycetemcomitans in most cases of A. actinomycetemcomitans-associated periodontitis.