The impact of diabetes on recurrent myocardial infarction (MI) and fatal coronary heart disease was examined in survivors of an initial MI using 34-year follow-up data in the Framingham Study. Among nondiabetic patients, the risk of fatal coronary heart disease was significantly lower in women compared with men (relative risk, 0.6). In the presence of diabetes, however, the risk of recurrent MI in women was twice the risk in men. In addition, the effect of diabetes doubled the risk of recurrent MI in women (relative risk, 2.1) but had an insignificant effect in men. Increased susceptibility to cardiac failure among diabetic women was an important factor in determining survivorship. Women with diabetes developed cardiac failure four times more often (16%) than women without diabetes (3.8%). Furthermore, when cardiac failure developed, 25% of diabetic women experienced a recurrent MI or fatal coronary event, more than doubling the rate when diabetes was absent. We conclude that in the diabetic patient who survives an MI, cardiac failure is a common occurrence, warranting early detection and vigorous management in periods of convalescence and follow-up. In addition, when cardiac failure appears, control of diabetes assumes added importance, particularly in women, where its effect on survivorship is considerable.