Both in CHF (congestive heart failure) and CRI (chronic renal insufficiency), blood pressure reduction is beneficial for preservation of cardiac and renal function. However, it is uncertain how much blood pressure reduction is appropriate in patients with both CHF and coexisting CRI. In the present study, we examined whether intensive blood pressure reduction is more beneficial in these patients than the usually accepted level of reduction. Thirty-five men and 21 women of average age 63+/-5 years suffering from both CHF and CRI were selected from 316 patients attending the Kidney Disease Center of Saitama Medical School Hospital. All participants had an ejection fraction (EF) of less than 55% as determined by echocardiography. Renal function was evaluated by 24-h creatinine clearance (GFR), and a GFR of less than 50 ml/min was regarded as indicating renal insufficiency. Patients were divided into 2 groups according to the target blood pressure: in group I, blood pressure (BP) was lowered to less than 120/75 mmHg and in group II, blood pressure was lowered to less than 130/80 but more than 121/76 mmHg. The daily doses of basic antihypertensive agents were amlodipine 5 to 20 mg, benazepril 2.5 to 5 mg, guanabenz 2 to 8 mg and furosemide 20 to 60 mg. At the end of a 2-year follow-up period, the BP in group I was controlled at the level of 118+/-4/73+/-3 mmHg with good maintenance of EF (46+/-4 to 60+/-4%) and GFR (44+/-4 to 40+/-3 ml/min). In group II, BP was maintained at 128+/-4/81+/-2 mmHg, accompanied by a reduction of EF (46+/-4 to 42+/-3%) and a significant reduction of GFR (44+/-3 to 35+/-3 ml/min). These results suggest that intensive blood pressure reduction might be beneficial in cases complicated by cardiorenal failure.