BACKGROUND: Cardiac disease is a common cause of death in chronic hemodialysis patients. A subanalysis of the data on cardiac diseases in the Hemodialysis (HEMO) Study was performed. The specific objectives were: (1) to analyze the prevalence of cardiac disease at baseline; (2) to characterize the incidence of various types of cardiac events during follow-up; (3) to examine the association of cardiac events during follow-up with baseline cardiac diseases; and (4) to examine the effect of dose and flux interventions on various types of cardiac events. METHODS: The HEMO Study is a randomized multi-center trial on 1846 chronic hemodialysis patients at 15 clinical centers comprising 72 dialysis units. The scheduled maximum follow-up duration was 0.9 to 6.6 years, with the mean actual follow-up of 2.84 years. The interventions were standard-dose versus high-dose and low-flux versus high-flux hemodialysis in a 2 x 2 factorial design. RESULTS: At baseline, 80% of patients had cardiac diseases, including ischemic heart disease (IHD) (39%), congestive heart failure (40%), arrhythmia (31%), and other heart diseases (63%). There were a total of 1685 cardiac hospitalizations, with angina and acute myocardial infarction accounting for 42.7% of these hospitalizations. There were 343 cardiac deaths during follow-up, accounting for 39.4% of all deaths. IHD was implicated in 61.5% of the cardiac deaths. Any cardiac disease at baseline was highly predictive of cardiac death during follow-up [relative risk (RR) 2.57; 95% CI 1.73-3.83]. There were no significant effects of dose or flux assignments on the primary outcome of all-cause mortality or the main secondary cardiac composite outcome of first cardiac hospitalization or all-cause mortality. Assignment to high-flux dialysis was, however, associated with decreased cardiac mortality and the composite outcome of first cardiac hospitalization or death from cardiac causes. CONCLUSION: The HEMO Study identified IHD to be a major cause of cardiac hospitalizations and cardiac deaths. Future strategies for the prevention of cardiac diseases in the maintenance hemodialysis population should focus on this entity. Although high-flux dialysis did not reduce all-cause mortality, it might improve cardiac outcomes. This hypothesis needs to be further examined.