Cardiovascular disease is delayed and less common in women than in men. Myocyte death occurs in heart failure, but only apoptosis has been documented; the role of myocyte necrosis is unknown. Therefore, we tested whether necrosis is as important as apoptosis and whether myocyte death is lower in women than in men with heart failure. Molecular probes were used to measure the magnitude of myocyte necrosis and apoptosis in 7 women and 12 men undergoing transplantation for cardiac failure. Myocyte necrosis was evaluated by detection of DNA damage with blunt end fragments, whereas apoptosis was assessed by the identification of double-strand DNA cleavage with single base or longer 3' overhangs. An identical analysis of these forms of cell death was performed in control myocardium. Heart failure showed levels of myocyte necrosis 7-fold greater than apoptosis in patients of both sexes. However, cell death was 2-fold higher in men than in women. Heart failure resulted in a 13-fold and 27-fold increase in necrosis in women and men, respectively. Apoptosis increased 35-fold in women and 85-fold in men. The differences in cell death between women and men were confirmed by the electrophoretic pattern of DNA diffusion and laddering of isolated myocytes. The lower degree of cell death in women was associated with a longer duration of the myopathy, a later onset of cardiac decompensation, and a longer interval between heart failure and transplantation. In conclusion, myocyte necrosis and apoptosis affect the decompensated human heart; each contributes to the evolution of cardiac failure. However, the female heart is protected, at least in part, from necrotic and apoptotic death signals.