BACKGROUND The association between periodontal disease and coronary artery disease (CAD) has been investigated in numerous studies with inconsistent results. Resolving these differences is complicated by the use of varying definitions of CAD. The aim of this study was to investigate the association between angiographically-defined CAD and periodontal disease. METHODS Non-smoking, non-diabetic patients, over 40 years of age, with no history of a myocardial infarction in the previous 6 months and who had undergone cardiac catheterization within the previous 12 months were enrolled in this study. Subjects were classified as having CAD (CAD+) if they had 50% stenosis in at least one major epicardial artery and classified as CAD negative (CAD-) if they had <50% stenosis in all identified arteries. Periodontal disease severity was measured through bleeding on probing, probing depth, clinical attachment level (CAL), gingival recession, number of missing teeth, and radiographic bone loss. RESULTS One hundred (53 = CAD+; 47 = CAD-) patients were examined. CAD+ patients were more likely to be male (CAD+ 83.0% male; CAD- 40.4% male; P= 0.001), and were older (CAD+ 65.3 years; CAD- 60.8 years; P= 0.0138). Although all patients reported they were currently non-smokers and had not smoked for at least 5 years, the fraction who were former smokers was greater for CAD+ patients (66% versus 24.4%; P = 0.0001) and mean pack/year history of smoking was higher for CAD+ patients (15.8 versus 4.5; P = 0.0003). Mean CAL (3.13 mm versus 2.78 mm; P 0.0227), number of sites with CAL > or = 6 mm (6.85 versus 3.32; P = 0.0242), radiographic bone loss (3.60 mm versus 3.18 mm; P = 0.0142) were greater for CAD+ patients than for CAD- patients. However, after adjustment for age and previous smoking history, factors common to both diseases, the associations of CAD and periodontal disease were reduced and were not statistically significant (odds ratio [OR]: mean CAL OR = 1.06; number of sites with CAL > or = 6 mm OR = 1.03; mean radiographic bone loss OR = 1.31; P > or = 0.2055). CONCLUSIONS After accounting for factors common to both periodontal disease and CAD, there was no significant association between periodontal disease and chronic CAD as assessed angiographically. Further investigations into the relationship between periodontal disease and CAD should clearly separate chronic CAD and acute coronary events.