Coronary artery disease (CAD) is the leading cause of death in many countries. The underlying mechanism of the chronic inflammatory process in atherosclerosis is still unknown. As a possible trigger, different viruses and bacteria may be associated with atherosclerotic diseases. The aim of this work was to investigate the association of chronic infection with C pneumoniae, H pylori and cytomegalovirus (CMV) infections and CAD. Fifty patients [20 with acute coronary artery disease (ACAD) and 30 with chronic coronary artery disease (CCAD)] in addition to 15 healthy individuals as a control group were involved in this study. The studied individuals were subjected to complete history taking, thorough physical examination, electrocardiography, echocardiography and coronary angiography (for patients). Assessment of blood glucose level, lipid profile and creatine kinase (CK) was performed. Determination of hsCRP was done by nephlemetry, while C pneumoniae-, H pylori- and CMV-specific IgG antibodies was done by enzyme immunoassay. Results showed that the levels of cholesterol, triglycerides, LDL-c and hsCRP were significantly higher, while HDL-c was significantly lower among patients compared to that of the controls. A significantly (P<0.05) higher perecentage of patients had C pneumoniae and H pylori-specific IgG antibodies as compared to that of the controls. Higher percentage of patients had CMV-specific IgG antibody, however, there was no significant difference between the 2 groups. The levels of C pneumoniae and H pylori-specific IgG antibodies were significantly (P<0.001) higher among patients with CAD when compared to that of the controls. CMV-specific IgG level in patients was higher compared to that of the controls, however, the difference was not statistically significant. Among acute CAD patients, C pneumoniae-specific IgG was positively correlated with hsCRP (P<0.05), cholesterol (p<0.01) and HDL-c (P<0.05), while H pylori-specific IgG was positively correlated with triglyceride level (P<0.05). Among patients with CCAD, hsCRP was negatively correlated with HDL-c (P<0.05). There was no significant correlation between the levels of CMV-specific IgG and lipid profile or hsCRP. In conclusion, the level of C pneumoniae and H pylori-specific IgG antibodies are elevated among CAD patients and their presence was associated with development of the disease. They were significantly correlated to cholesterol level. Moreover, C pneumoniae-specific IgG was significantly correlated with hsCRP among ACAD patients, suggesting an important role of these organisms in the development of CAD by altering lipid profile and induction of inflammation.