Objectives: To investigate whether there is a relationship between levels of C-reactive protein (CRP), coronary heart disease (CHD) and periodontitis in males in Northern Ireland (NI). Methods: Cases were males aged over 40 years with coronary artery disease evidenced by >50% narrowing of at least one coronary artery on angiography or Thallium radioisotope scanning. Controls were age-matched males, randomly drawn from the general population of our hospital’s catchment area. Each subject had a clinical periodontal examination and completed a detailed socio-demographic questionnaire. Subjects with pocketing of 6mm or deeper were ajudged to have chronic periodontitis (CP). High sensitivity CRP was measured in serum by an automated enzyme assay. The Mann Whitney test and Chi square analysis were used as appropriate with a CRP value of >2mg/L categorised as high. Results: There was considerable variability in the CRP values. The cardiac group had slightly higher levels (mg/L) of CRP (median 1.63, IQR 2.54) than the controls ( median 1.54, IQR 1.62 ), z=0.95, P=0.34. Those with periodontitis had higher levels of CRP (median 2.11, IQR 2.85) than those with no periodontitis (median 1.45, IQR 1.68), z=2.42, P=0.016. A higher proportion of those with high CRP (58%) had CP compared with only 31% of those without CP, Chi square 8.43, P=0.004. Within the cardiac group 59% of those with high CRP also had CP compared with only 34% of those without CP, Chi square 4.74, P=0.029. In the control group 56% of those with high CRP had CP compared with 29% of those without CP, Chi square 2.5, P= 0.11. Conclusions: Clinical evidence of periodontitis was associated with higher levels of CRP in this sample of Northern Ireland males. Supported by the Northern Ireland Chest Heart and Stroke Association.