BACKGROUND The burden of cardiovascular disease world-wide is one of great concern to patients and health care agencies alike. Cardiac rehabilitation aims to restore patients with heart disease to health through exercise only based rehabilitation or comprehensive cardiac rehabilitation. OBJECTIVE To determine the effectiveness of exercise only or exercise as part of a comprehensive cardiac rehabilitation programme on the mortality, morbidity, health-related quality of life (HRQoL) and modifiable cardiac risk factors of patients with coronary heart disease. METHODS Electronic databases were searched for randomised controlled trials, using standardised trial filters, from the earliest date available to December 31st 1998. METHODS Men and women of all ages, in hospital or community settings, who have had myocardial infarction, coronary artery bypass graft or percutaneous transluminal coronary angioplasty, or who have angina pectoris or coronary artery disease defined by angiography. METHODS Studies were selected independently by two reviewers, and data extracted independently. Authors were contacted where possible to obtain missing information. RESULTS This systematic review has allowed analysis of an increased number of patients from approximately 4500 in earlier meta-analyses to 8440 (7683 contributing to the total mortality outcome). The pooled effect estimate for total mortality for the exercise only intervention shows a 27% reduction in all cause mortality (random effects model OR 0.73 (0.54, 0.98)). Comprehensive cardiac rehabilitation reduced all cause mortality, but to a lesser degree (OR 0.87 (0.71, 1.05)). Total cardiac mortality was reduced by 31% (random effects model OR 0.69 (0.51, 0.94)) and 26% (random effects model OR 0.74 (0.57, 0.96)) in the exercise only and comprehensive cardiac rehabilitation groups respectively. Neither intervention had any effect on the occurrence of non-fatal myocardial infarction. There was a significant net reduction in total cholesterol (pooled WMD random effects model -0.57 mmol/l (-0.83, -0.31)) and LDL (pooled WMD random effects model -0.51 mmol/l (-0.82, -0.19) in the comprehensive cardiac rehabilitation group. CONCLUSIONS Exercise-based cardiac rehabilitation is effective in reducing cardiac deaths. It is not clear from this review whether exercise only or a comprehensive cardiac rehabilitation intervention is more beneficial. The population studied in this review is still predominantly male, middle aged and low risk. Identification of the ethnic origin of the participants was seldom reported. It is possible that patients who would have benefited most from the intervention were excluded from the trials on the grounds of age, sex or co-morbidity.