The present invention relates to cardiac hypertrophy. More particularly, the present invention defines the molecular events linking calcium stimulation to cardiac hypertrophy. More specifically, the present invention shows that Ca.sup.2+ stimulation of the hypertrophic response is mediated through an HDAC 4 and 5 interaction with MEF2, and that phosphorylation of HDACs results in loss of HDAC-mediated repression of MEF2 hypertrophic action. Thus, the present invention provides methods and compositions of treating cardiac hypertrophy, as well as methods and compositions for identifying subjects at risk for cardiac hypertrophy. Further provided are methods for the detection of compounds having therapeutic activity toward cardiac hypertrophy.