To search for bacterial DNA sequences in cholesterol gallstones with negative bacterial culture. We used nested primers polymerase chain reaction (NP-PCR) technique to amplify bacterial gene fragments were amplified in vitro from DNA extracted from cholesterol gallstones. Comparative 16S ribosomal RNA sequence analysis was used for elucidation of bacterial identification. The gallbladder gallstones of 30 patients were analyzed. Bacterial DNA was found in the stones of 26 patients. There was no difference either in cholesterol and water content or in harboring bacterial DNA of gallstones. E. coli-related DNA fragments were found in the stones of 8 patients (26.67%). Propionibacteria type DNA was found in the stones of 7 patients (23.33%). Stones of 2 patients (6.67%) harbored bacterial gene fragments with similarity of Streptococcus pyogenes. A more heterogeneous sequence collection was found in 7 patients (23.33%) and could be assigned to the multiple bacterial infections. Another stones of 2 patients (6.67%) had bacterial DNA with lower molecularweight which might be related to some unidentified bacteria. The results suggested that most cholesterol gallstones harbor bacterial DNA. It is important to determine whether these microorganisms are innocent bystanders or active participants in cholesterol gallstone formation.