BACKGROUND: Cardiac resynchronization therapy (CRT) is a promising new treatment for patients with heart failure and cardiac dyssynchrony. The CARE-HF study is a morbidity/mortality trial designed to provide conclusive evidence of the effects of CRT in patients with moderate to severe heart failure. METHODS: A description of the baseline characteristics of patients randomised in the CARE-HF trial. RESULTS: 813 Patients with predominantly NYHA class III (94%) heart failure were randomised in 82 centres. Their mean age was 65 (interquartile range [IQR] 59 to 72) years, 34% were aged >70 years and 27% were women. Thirty-eight percent of the patients had ischaemic heart disease. Mean heart rate was adequately controlled at 70 (IQR 60 to 78) bpm consistent with the use of beta-blockers. Supine systolic blood pressure was low at 117 (IQR 105 to 130) mm Hg. Eighty-eight percent of patients had a QRS > or =150 ms. Mean LV ejection fraction was 26% (IQR 22 to 29) and end-diastolic dimension was 7.2 (IQR 6.4 to 7.8) cm. Ninety-four percent of patients were receiving loop diuretics, 95% an ACE inhibitor or angiotensin receptor blocker (ARB), 72% a beta-blocker and 56% were taking spironolactone. CONCLUSIONS: The patients enrolled in CARE-HF had moderately severe heart failure and cardiac dysfunction with evidence of cardiac dyssynchrony. The population appears at high risk of events despite pharmacological therapy and therefore appropriate for a trial of CRT.