As cardiac hypertrophy develops, total cardiac RNA and protein synthesis increase significantly. We have identified specific messenger RNAs that change in predominance with the induction of pressure-overload-stimulated cardiac hypertrophy. Total cardiac RNA was isolated from rats either undergoing cardiac hypertrophy secondary to subdiaphragmatic aortic constriction or subjected to sham surgery. The products translated in vitro were separated by two-dimensional gel electrophoresis and quantitated. The translation of four proteins decreased while the translation of four others increased in preparations from hypertrophied hearts compared with those from sham-treated rats. Two isoforms of creatine kinase M were translated in vitro. Only one of these isoforms decreased with cardiac hypertrophy, suggesting that the transcriptional or translational control for creatine kinase is much more complex than previously believed. Finally, since only eight of over 700 different translation products changed in relative predominance with cardiac hypertrophy, we conclude that the accumulation of existing RNA and protein products is the primary adaptive process responsible for cardiac hypertrophy.