Disease of the venous system is a major problem affecting western societies, resulting in considerable morbidity in the population and cost to the health service. In many countries "varicose veins are probably the commonest disorder presenting to general surgeons" and an average of 30% of district nursing time is estimated to be spent caring for patients with venous ulcers. For the patient with varicose veins or leg ulceration, there is often persistent discomfort and disability extending over long periods of time. Despite this, little epidemiological research has been carried out on venous disease, perhaps partly because of society's perception that venous disease is not a major problem and it is not normally a cause death. More recently however, efforts have been made to conduct structured epidemiological studies to identify risk factors and to clarify the geographical variations suggested in the past by anecdotal evidence. This article reviews recent epidemiological studies, discusses the prevalence of varicose veins and presents evidence for and against the differing theories of causation.