Background: Periodontitis and coronary heart disease are both triggered by inflammatory response which is influenced by the genetic predisposition. The c.-874T>A polymorphism in interferon-g (IFN-g) has been associated with altered cytokine production. Patients and methods: A total of 960 consecutive patients with angiographic proven coronary heart disease (no or mild periodontitis: n=493, severe periodontitis: n=447) were prospectively included in the study entitled "Periodontitis and Its Microbiological Agents as Prognostic Factors in Patients with Coronary Heart Disease". In this subanalysis, the c.-874T>A polymorphism in IFN-g was analyzed by CTS-PCR-SSP Tray kit (Heidelberg, Germany). Subgingival bacterial colonization (11 bacteria) was assessed using a polymerase chain reaction (PCR)/DNA probe test (micro-Ident®). Results: The genotype (p=0.987) and allele frequencies (p=0.860) of the c.-874T>A polymorphism in IFN-g were not proven to be as risk indicators for the severity of periodontitis in patients with coronary heart disease. However, AA-genotype and A-allele carriers had a decreased risk for subgingival occurrence of P. intermedia (genotype: p=0.006, allele: p=0.01) and E. corrodens (genotype: p=0.034, allele: p=0.013). These associations remained significant after forward stepwise binary logistic regression analyses considering age, gender, smoking, diabetes, plaque index as potential confounders. Conclusions: Despite the genetic background of IFN-g could be shown to be associated with subgingival colonization of P. intermedia and E. corrodens there is no evidence that it is an independent risk indicator for severity of periodontitis in coronary patients. Keywords: interferon-g, SNP, periodontitis heart disease