The purpose of this study was to examine the relationship between clinical findings and subgingival microbial flora in periodontitis. The results obtained were as follows: 1. In a phase-contrast microscopic study, no correlation was found between the clinical findings, total bacteria or proportional distribution of spirochetes or motile rods in the periodontal pocket. 2. Anaerobic incubation revealed no correlation between clinical findings, total bacteria or proportional distribution of black-pigmented Bacteroides in the periodontal pocket.