Context Although Chlamydia pneumoniae infection has been associated with the initiation and progression of atherosclerosis, results of clinical trials investigating antichlamydial antibiotics as adjuncts to standard therapy in patients with coronary artery disease (CAD) have been inconsistent. Objective To conduct a meta-analysis of clinical trials of antichlamydial antibiotic therapy in patients with CAD. Data Sources The MEDLINE and Cochrane Central Register of Controlled Trials databases were searched from 1966 to April 2005 for English-language trials of antibiotic therapy in patients with CAD. Bibliographies of retrieved articles were searched for further studies. Presentations at major scientific meetings (2003-2004) were also reviewed. Search terms included antibacterial agents, myocardial infarction, unstable angina, and coronary arteriosclerosis. Study Selection Eligible studies were prospective, randomized, placebo-controlled trials of antichlamydial antibiotic therapy in patients with CAD that reported all-cause mortality, myocardial infarction, or unstable angina. Of the 110 potentially relevant articles identified, 11 reports enrolling 19217 patients were included. Data Extraction Included studies were reviewed to determine the number of patients randomized, mean duration of follow-up, and end points. End points of interest included all-cause mortality, myocardial infarction (MI), and a combined end point of Ml and unstable angina. Data Synthesis Event rates were combined using a random-effects model. Antibiotic therapy had no impact on all-cause mortality among treated vs untreated patients (4.7% vs 4.6%; odds ratio [OR], 1.02; 95% confidence interval [Cl], 0.89-1.16; P=.83), on the rates of MI (5.0% vs 5.4%; OR, 0.92; 95% Cl, 0.81 -1.04; P=.19), or on the combined end point of MI and unstable angina (9.2% vs 9.6%; OR, 0.91; 95% Cl, 0.76-1.07; P=.25). Conclusion Evidence available to date does not demonstrate an overall benefit of antibiotic therapy in reducing mortality or cardiovascular events in patients with CAD.