The different forms of periodontitis are all associated with a distinct bacterial flora. However, a clear relationship is described between localized juvenile periodontitis (LJP) and Actinobacillus actinomycetemcomitans. Eleven LJP patients all harboured A. actinomycetemcomitans. The arrest of LJP is often impossible, due to the inability to eliminate A. actinomycetemcomitans. Therefore, antibiotic treatment was introduced in combination with the initial treatment. We studied the effect of periodontal treatment on the microflora and clinical status of periodontal disease patients using different therapies. Group 3 attained the best results (initial treatment and a combination metronidazole and amoxicillin), the group to eliminate A. actinomycetemcomitans effectively.