Abstract Inhabitants of Túquerres in the Colombian Andes have a 25-fold higher risk of gastric cancer than inhabitants of the coastal town Tumaco, despite similar H. pylori prevalences. The gastric microbiota was recently shown in animal models to accelerate the development of H. pylori -induced precancerous lesions. 20 individuals from each town, matched for age and sex, were selected and gastric microbiota analyses were performed by deep sequencing of amplified 16S rDNA. In parallel, analyses of H. pylori status, carriage of the cag pathogenicity island and assignment of H. pylori to phylogeographic groups were performed to test for correlations between H. pylori strain properties and microbiota composition. The gastric microbiota composition was highly variable between individuals, but showed a significant correlation with the town of origin. Multiple OTUs were detected exclusively in either Tumaco or Túquerres. Two operational taxonomic units (OTUs), Leptotrichia wadei and a Veillonella sp. , were significantly more abundant in Túquerres and 16 OTUs, including a Staphylococcus sp. were significantly more abundant in Tumaco. There was no significant correlation of H. pylori phylogeographic population or carriage of the cag PAI with microbiota composition. From these data, testable hypotheses can be generated and examined in suitable animal models and prospective clinical trials.