Apoptosis is involved in transition from compensated cardiac hypertrophy to heart failure which is accompanied by an induction of TGFb/SMAD signalling pathway. The use of effective SMAD inhibitors may protect the heart against heart failure progression. The transcription factor YB-1 mediates inhibitory effects on genes associated with cell death and interacts with SMAD transcription factors. The question arises whether overexpression of YB-1 can influence TGFb induced apoptosis and how a-adrenergic hypertrophy is affected by YB-1. Therefore, we infected isolated cardiomyocytes (CM) with an adenovirus (AdYB-1) and analyzed the effect of YB-1 on apoptosis and hypertrophy induction in these cells. TGFb1 induced apoptosis while overexpression of YB-1 prevented this induction. TGFb1 caused a significant increase of phosphorylated SMADs in CM after overexpression of YB-1 demonstrating that activation of SMAD transcription factors are not inhibited by YB-1 overexpression. Inhibition by YB-1 may be accomplished by interaction of SMAD/TGFb signalling with activated SMADs. In respect to hypertrophy, after stimulation with a-adrenoceptoragonist phenylephrine (PE) a significant enlargement of cell cross-sectional-area and rate of protein-synthesis was observed in non-infected CM. Infection of CM with AdYB-1 blocked the PE induced hypertrophy. Conclusion: We identified YB1 as a repressor of both apoptosis and hypertrophy in cardiomyocytes. YB-1 therefore provides new perspectives for therapeutic approaches against heart failure progression.