We evaluated the prognostic value of renal function in an initially "untreated" population with mild heart failure and compared the prognosis of this population with a matched controlled population. During a follow-up of 13 years (mean 11.7), 90 patients (56%) died. Mortality was higher compared with a matched controlled population. Multivariate Cox regression analysis demonstrated that beside the well-established risk markers of left ventricular ejection fraction and heart rate, renal function (estimated glomerular filtration rate, hazard ratio 1.16/10 ml/min/1.73 m(2), p = 0.003) was the only additional independent predictor of cardiovascular mortality in patients with early heart failure.