We tested the hypothesis that activation of protein kinase C (PKC) isoforms in pressure-overload heart failure was prevented by angiotensin-converting enzyme (ACE) inhibition, resulting in normalization of cardiac sarcoplasmic reticulum (SR) Ca²⁺ ATPase (SERCA) 2a and phospholamban protein levels and improvement in intracellular Ca²⁺ handling. Aortic-banded and control guinea pigs were given ramipril (5 mg · kg¹ · day¹) or placebo for 8 wk. Ramipril-treated banded animals had lower left ventricular (LV) and lung weight, improved survival, increased isovolumic LV mechanics, and improved cardiomyocyte Ca²⁺ transients compared with placebo-treated banded animals. This was associated with maintenance of SERCA2a and phospholamban protein expression. Translocation of PKC- and - was increased in placebo-treated banded guinea pigs compared with controls and was attenuated significantly by treatment with ramipril. We conclude that ACE inhibition attenuates PKC translocation and prevents downregulation of Ca²⁺ cycling protein expression in pressure-overload hypertrophy. This represents a mechanism for the beneficial effects of this therapy on LV function and survival in heart failure.