Goals: We aimed to investigate the presence of bacterial structures in choles terol gallstones and particularly presence of Helicobacter spp/H. pylori in gall stones by microbiologic cultivation, histopathologic staining, and polymerase ch ain reaction (PCR). Background: Many studies suggest that different mechanisms a re responsible for the formation of pigmented gallstones and cholesterol gallsto nes. Recently, studies showed that infection could have an important role in the formation of cholesterol gallbladder stones. Study: We examined 77 mixed choles terol gallstones. After cholecystectomy, gallbladder cultures were done for H. p ylori and other bacterium. Gallbladder has also been examined by three histopath ologic staining methods (Warthin- Starry, hematoxylin eosin, and gram staining) for Helicobacter spp. In addition, 16S rRNA- PCR amplification was performed f or Helicobacter spp in gallstones. Twenty postmortem gallbladders without gallst ones were investigated by the same histopathologic and PCR methods for Helicobac ter spp. as a control group. Results: Different bacterium were isolated from 22 gallbladder samples (12 Escherichia coli, 8 Pseudomonas, and 2 clostridium) and H. pylori was isolated in 6 gallbladder samples. Helicobacter spp was found in 7 gallstones by PCR amplification. Helicobacter- like organisms were demonstrate d in 18 samples by three different histopathologic methods. Helicobacter- like organisms were also found in five samples by the same histopathologic methods (W arthin- Starry, hematoxylin- eosin, and gram staining). Only four samples were found positive for Helicobacter spp/H. pylori by all methods. Conclusions: Bact erial population including H. pylori could have a possible role in the formation of cholesterol gallstones. Goals: We aimed to investigate the presence of bacterial structures in choles terol gallstones and particularly presented in Helicobacter spp / H. Pylori in gall stones by microbiologic cultivation, histopathologic staining, and polymerase chin reaction (PCR). Background: Many studies suggest that different mechanisms a re responsible for the formation of pigmented gallstones and cholesterol gallsto nes. Recently, studies showed that infection could have an important role in the formation of cholesterol gallbladder stones. Study: We examined 77 mixed choles terol gallstones. After cholecystectomy, gallbladder cultures were done for H. p ylori and other bacterium. Gallbladder has also been examined by three histopath ologic staining methods (Warthin-Starry, hematoxylin eosin, and gram staining) for Helicobacter spp. In addition, 16S rRNA- Helicobacter spp in gallstones. Twenty postmortem gallbladders without gallst ones were investigated by the same histopathologic and PCR methods for Helicobacter spp. as a control group. Results: Different bacterium were isolated from 22 gallbladder samples (12 Escherichia coli, 8 Pseudomonas, and 2 clostridium) and H. pylori was isolated in 6 gallbladder samples. Helicobacter spp was Helicobacter-like organisms were demonstrated in d samples with three different histopathologic methods. Helicobacter-like organisms were also found in five samples by the same histopathologic methods (W arthritis - Starry, hematoxylin-eosin, and Only four samples were found positive for Helicobacter spp / H. pylori by all methods. Conclusions: Bact erial population including H. pylori could have a possible role in the formation of cholesterol gallstones.