From an epidemiological point of view, at least three different entities of chronic venous insufficiency (CVI) can be defined: heavy legs syndrome is experienced by about half the working people of industrialized countries. It is most frequently linked to varicosis, nevertheless, in one case out of three, no venous incompetence is associated. Female sex, prolonged standing position and overweight are other significant risk factors; varicosis comes with modern civilization. Its prevalence is very low in African and Asian or Australasian aborigen populations although immigrant subjects from these regions have the same risk as the population of their host country. Sedentarity, overweight, tight clothing may provide part of the explanation. But the main factor is probably linked to the low fiber diet in industrialized countries through induced constipation and increased abdominal pressure, or because of the associated low vitamin F intake. Varicosis is rarely seen before adulthood, and its prevalence increases with aging. Sex ratio is unbalanced (F/M estimates: 1.5 to 3.5), that is mainly explained by childbearing and hormonal gactors. A familial factor has also been evidenced, with a relative risk of 2, when one parent has varicosis, and about 3 when both are involved; epidemiological data regarding cutaneous trophic changes in CVI are restricted to leg ulcers: 1% of the general population, and 4 to 5% of people aged 80 and more are afflicted. Leg ulcers are frequently found in the post-thrombotic syndrome, but female sex and varicosis are other significant risk factors. Up to now, epidemiological data are too scarce for a definite demonstration of the natural history of the different subsets of CVI. On the other hand, they clearly show that major medical, social and economical problems are involved.