To determine the presence of Helicobacter pylori and, if detected, the prevalence of the CagA gene in adenotonsillectomy specimens by polymerase chain reaction (PCR).A prospective clinical trial.Tertiary referral center.The study population comprised 23 patients who had undergone adenoidectomy, tonsillectomy, or adenotonsillectomy under local or general anesthesia. Helicobacter pylori DNA was extracted from 3-mm-diameter tissue samples obtained from each tonsil and adenoid tissue specimens. The amplifications were performed for the 16S ribosomal RNA (rRNA) and CagA genes of H pylori in the samples of which H pylori DNA was detected.In examining all the samples, 7 (30%) of 23 patients were shown to be positive for H pylori DNA, 5 (71%) of whom also possessed the CagA gene.Tonsil and adenoid tissues may be an ecological niche of the mouth without regard to transient or permanent colonization. Oral-oral transmission may be a possible mode of spread of H pylori.