Renal dysfunction is a frequent and progressive complication of chronic heart failure and is a powerful predictor of cardiovascular mortality. It is intimately associated with cardiovascular disease even in its earliest stages. Although cardiovascular and renal disease share many risk factors, the prognostic implications do not simply reflect widespread atherosclerotic vascular disease as this appears to be as important in those with heart failure secondary to idiopathic dilated cardiomyopathy as it is in those with coronary artery disease. There may be a role in the progression of heart failure, as the deleterious effects of even "mild" renal impairment seem to be borne out in predicting outcome, in a broad range of heart failure patients including those with heart failure and preserved systolic function. Renal dysfunction is both an indication for, as well as frequently limiting intervention with intensive disease modifying therapy. Although renal impairment is common in heart failure and these patients are at higher risk for adverse events including death, they are under represented in clinical trials.