It is now widely accepted that two forms of cell death, apoptosis and necrosis, occur in cardiomyocytes, and increasing evidence indicates that apoptosis plays an important role in the pathophysiology of cardiovascular diseases. Currently, two major pathways in the induction of apoptosis are known to occur in cardiomyocytes, the mitochondrial pathway and the death receptor pathway. Bcl-2 family proteins are key regulators of apoptosis in the mitochondrial pathway. Among them, Bcl-x(L), which is structurally similar to Bcl-2 and functions as an antiapoptotic molecule, is involved in diseases such as ischemic heart diseases and heart failure. In this review, we focus on the role of Bcl-x(L) in apoptosis in cardiomyocytes and discuss the potential use of Bcl-x(L) as a cardioprotective therapy for cardiac diseases.