Purpose: The antineoplastic anthracycline doxorubicin can induce a dose-dependent cardiomyopathy that limits the total cumulative dose prescribed to cancer patients. In both preclinical and clinical studies, pretreatment with dexrazoxane, an intracellular iron chelator, partially protects against anthracycline-induced cardiomyopathy. To identify potential additional cardioprotective treatment strategies, we investigated early doxorubicin-induced changes in cardiac gene expression. Methods: Spontaneously hypertensive male rats (n = 47) received weekly intravenous injections of doxorubicin (3 mg/kg) or saline 30 min after pretreatment with dexrazoxane (50 mg/kg) or saline by intraperitoneal injection. Cardiac samples were analyzed 24 h after the first (n = 20), second (n = 13), or third (n = 14) intravenous injection on days 1, 8, or 15 of the study, respectively.Results: Rats receiving three doses of doxorubicin had minimal myocardial alterations that were attenuated by dexrazoxane. Cardiac expression levels of genes associated with the Nrf2-mediated stress response were increased after a single dose of doxorubicin, but not affected by cardioprotectant pretreatment. In contrast, an early repressive effect of doxorubicin on transcript levels of genes associated with mitochondrial function was attenuated by dexrazoxane pretreatment. Dexrazoxane had little effect on gene expression by itself.Conclusions: Genomic analysis provided further evidence that mitochondria are the primary target of doxorubicin-induced oxidative damage that leads to cardiomyopathy and the primary site of cardioprotective action by dexrazoxane. Additional strategies that prevent the formation of oxygen radicals by doxorubicin in mitochondria may provide increased cardioprotection.