Background: Previous studies have demonstrated that renal dysfunction is common in patients with heart failure (HF), but it is not known whether chronic kidney disease (CKD) is associated with increased risks of long-term adverse outcomes in unselected HF patients encountered in current routine clinical practice in Japan. Methods and Results: The Japanese Cardiac Registry of Heart Failure in Cardiology (JCARE-CARD) prospectively studied a broad sample of patients hospitalized with worsening HF and their outcomes with an average of 2.4 years of follow-up. The study cohort (n=2,013) were classified into 3 groups by estimated glomerular filtration rate (eGFR): ≥60 (n=579), 30-59 (n=1,025), and <30 ml · min^-1 · 1.73 m^-2 or patients with dialysis (n=409); 1,372 patients (70.3%) had an eGFR <60 ml · min^-1 · 1.73 m^-2 and 62 patients were treated with dialysis. The multivariable adjusted risk for all-cause death or rehospitalization increased with reduced eGFR; an adjusted hazard ratio (HR) 1.520 (95% confidence interval (CI) 1.186-1.949) for eGFR 30-59 ml · min^-1 · 1.73 m^-2 (P=0.001) and HR 2.566 (95%CI 1.885-3.492) for eGFR <30 ml · min^-1 · 1.73 m^-2 or patients with dialysis (P<0.001). Conclusions: CKD is common in HF and was independently associated with long-term adverse outcomes in a broad cohort of Japanese patients. (Circ J 2009; 73: 1442 - 1447)