Coronary heart disease remains the leading cause of death in postmenopausal women around the world, and interest is high in discovering the best treatments and methods of prevention for this disease. For many years, it appeared that one such treatment could be oestrogen, because of its beneficial effects on the vascular endothelium and on cholesterol concentrations. However, recent clinical trials have shown no beneficial effect of long-term hormone replacement therapy (HRT) on risk for major cardiovascular events among women with established coronary disease. These surprising findings have led to still further analyses to elucidate plausible explanations. This paper will review the results from recent trials and clinical studies of HRT, as well as ongoing trials that continue to examine the role of oestrogen in the treatment and prevention of cardiovascular disease.