Capillary functions in humans can be assessed by measuring capillary filtration and capillary diffusion capacity in the extremities. Examination of these two parameters supplements each other and renders it possible to evaluate capillary function from different aspects. As an example of practical use may serve the findings in patients with obliterating atherosclerosis of the lower extremities and in subjects with chronic venous insufficiency. The authors revealed a rised capillary diffussion capacity on obliterated extremities and a reduced capillary filtration in venous insufficiency. It is possible that in both instances these are manifestations of adaptational changes focused on the prevention of oedema formation and on a raised metabolism under conditions of an inadequate blood supply of tissues.