Heart failure is now recognised as a major and escalating public health problem in industrialised countries with ageing populations. Any attempt to describe the epidemiology, aetiology, and prognosis of heart failure, however, must take account of the difficulty in defining exactly what heart failure is. Though the focus of this article is the symptomatic syndrome it must be remembered that as many patients again may have asymptomatic disease that might be legitimately labelled “heart failure”—for example, asymptomatic left ventricular systolic dysfunction. More comprehensive reviews of the epidemiology and associated burden of heart failure have been published by McMurray and colleagues1 and more recently by Cowie and colleagues.2

Data relating to the aetiology, epidemiology and prognostic implications of heart failure are principally available from five types of studies:

• Cross sectional and longitudinal follow up surveys of well defined populations. These have almost exclusively focused on those individuals with clinical signs and symptoms indicative of chronic heart failure.

• Cross sectional surveys of individuals who have been medically treated for signs and symptoms of heart failure within a well defined region.

• Echocardiographic surveys of individuals within a well defined population to determine the presence of left ventricular systolic dysfunction.

• Nation wide studies of annual trends in heart failure related hospitalisation identified on the basis of diagnostic coding at discharge.

• Comprehensive clinical registries collected in conjunction with clinical trials. These include a large proportion of individuals who were identified on the basis of having both impaired left ventricular systolic dysfunction and signs and symptoms of heart failure.

Within the context of the specific limitations of the type of data available from these studies, the current understanding of the aetiology, epidemiology, and prognostic implications of chronic heart failure are discussed here.