For the management of chronic heart failure, both angiotensin converting enzyme inhibitors (ACEI) and angiotensin II type 1 receptor blockers (ARB) are useful, however, the differences between the two groups of agents are unclear. We compared the effects of long-term treatment with an ACEI (imidapril) and an ARB (TA-606) in rats that had recovered from experimental autoimmune myocarditis (EAM). Forty-two Lewis rats were immunized with porcine cardiac myosin on day 0 and divided into 6 groups, group C (distilled water), group IL (imidapril 0.5 mg/kg/day), group IH (imidapril 2 mg/kg/day), group TL (TA-606 2 mg/kg/day), group TH (TA-606 6 mg/kg/day), and group IT (imidapril 0.5 mg/kg/day + TA-606 2 mg/kg/day). Drugs were administered from day 28. Hemodynamic parameters, heart weight/body weight ratio (HW/BW), and area of fibrosis were measured on days 70-74. Only the high dose of imidapril significantly decreased central venous pressure and significantly increased maximum dP/dt and the absolute value of minimum dP/dt. HW/BW was suppressed in groups IH, TH, and IT. Thus, in treatment of chronic heart failure in rats, a sufficient dose of ACEI was needed to improve hemodynamics and to prevent ventricular hypertrophy. The hemodynamic effects of ARB and combination therapy of both drugs at low doses were not significant.