Peripheral arterial occlusive disease (PAOD) is a clinical syndrome that encompasses different nosological entities which are characterized in common by the reduced blood supply to the lower arteries. Its prevalence is rising steadily in Western countries and PAOD is thus coming to play an ever wider and more important role at social level. The epidemiology shows a progressively growing incidence of PAOD with the increase in the aging of the population. This article looks at the different disease classifications currently in use and the functional assessments for PAOD, which are based on ankle pressure measurements and intermittent claudicatio evaluations.