Objective To investigate the effects of chronic periodontitis on heart attack and stability of coronary artery disease (CAD). Methods Number of missed teeth was recorded and periodontal index evaluated in 266 patients with CAD, including 72 cases of acute mycocardial infarction (AMI sub-group), 91 cases of unstable angina pectoris (UAP sub-group) and 103 cases of stable angina pectoris (SAP sub- group ), and 266 healthy controls. Comparison was made between the both groups and between each sub-group and controls. Results Periodontal index in CAD group was higher than that in control group ( P 0.05). Conclusions Chronic periodontitis can affect heart attack and stability of CAD, which may be an independent risk factor for CAD.