A study on the predominant cultivable microorganisms inhabiting gingival crevices affected with a chronic gingivitis was carried out using the roll tube culture technique. Samples were obtained from nine individuals 25--42 years of age. Gram-positive rods make up 29.1% of the isolates and included mainly Actinomyces naeslundii, Actinomyces israelii, and Actinomyces viscosus. Streptococcus mitis and Streptococcus sanguis together made up 26.8% of the cultivable organisms. Peptostreptococcus averaged 3.0% of the organisms recovered. Gram-negative anaerobic rods constituted 25.0% of the total isolates with Fusobacterium nucleatum, Bacteroides melaninogenicus ss. intermedius. Bacteriodes ochraceus, other Bacteroides species, Selenomonas sputigena, and Campylobacter sputorum as the most predominant isolates. Haemophilus parainfluenzae averaged about 14% and Veillonella species 4.3% of the cultivable microflora. The data presented indicate that the subgingival microflora of a chronic gingivitis differs from those of healthy periodontium and advanced adult and juvenile periodontis. This might suggest that different infectious processes may be operative in various clinical entities of periodontal disease.