THIS STUDY EXAMINED THE EFFECT Of Oral food consumption on the prevalence and levels of subgingival bacteria and yeasts in 20 gastrostomy tube-fed children and 24 healthy controls. Microbial identification was carried out using anaerobic culture and 16S rRNA-based PCR identification methods. Streptococcal and Actinomyces species were recovered from 100% and 76% of all subjects and averaged 66% and 11% of total cultivable organisms, respectively. In decreasing order of prevalence, Fusobacterium, enteric rods, Prevotella intermedia/Prevotella nigrescens, Capnocytophaga, Propionibacterium, yeasts, Actinobacillus actinomycetemcomitans, coagulase-negative Staphylococcus, Campylobacter rectus, Bacteroides forsythus, and Porphyromonas gingivalis were detected in 48% to 2% of the study subjects. The cultivable levels of these species varied widely among subjects. PCR detection showed C. rectus and Eikenella corrodens both to occur in 93% of the study subjects and to be the most prevalent putative periodontal pathogens examined. In decreasing order of prevalence, PCR identified Treponema denticola, A. actinomycetemcomitans, P. nigrescens, P. intermedia, B. forsythus, and P. gingivalis in 38% to 21% of the subjects studied. Tube-fed children and healthy controls exhibited similar subgingival microbial compositions. It appears from this study that oral food consumption is not a major determinant for the establishment of subgingival microbiota in children.