The frequencies and proportions of predominant cultiv ableoral bacteria associated with 49 healthy children and juvenile (6-25 yr old) were studied. A total of 72 bacterial species belonging to 28 genus were detected in 195 samples of saliva, fissure plaque, supragingival plaque, and subgingival plaque. The predominant bacteria were Oral streptococci, Neisseria, Actinomyces, Capnocytophaga, Bacteroides and Fusobacterium in the normal oral cavity of healthy children and juvenile. There were differences in the distribution of the predominant flora, e.g. Fusobacterium and Bacteroides had higher incidence and proportion in the subgingival plaque than in the fissure plaque.