Although an enrichment of orally derived bacteria is reported in the gut microbiota of patients with several diseases, it is mostly unknown whether oral bacteria can colonize and induce intestinal inflammation. In a recent paper in Science, Atarashi et al.1 from Kenya Honda's laboratory show that a subset of orally derived bacteria colonizes and persists in the gut, leading to activation of the intestinal immune system and subsequent chronic inflammation in a susceptible host. The impact of oral health status as a potential contributor to inflammatory diseases at distal sites of the body deserves consideration.