Acute diseases of the veins, in most cases thromboses, cause inability to work in almost all cases; in profound phlebothromboses hospital treatment is indicated. In the chronic venous insufficiency the functional capacity can be decreased especially bey pains, inclination to swelling and changes of the skin (congestive dermatoses, ulcera). Eventual basic diseases and concomitant diseases render the judgment difficult. Experienced treatment under active collaboration of the patient may improve the functional capacity in most cases. The daily load of the patient by profession and so on, and the often changing course of chronic diseases of the veins must be taken into consideration in the estimation. On the basis of a stage-plan proposed by Kornotzki and coworders the evidence of selected phlebological methods (anamnesis, state, tourniquet-tests, measurement of the venous pressure, functional phlebography) is discussed. It is particularly referred to plethysmographic functional tests of the veins.