The light reflexion rheography is described as non-invasive investigation method for the venous system. The basic principle of the method and its applications are explained as well as its evaluation and the peculiarities which are to be taken into consideration thereby are discussed in detail. The comprising evaluation of the haemodynamic changes in chronic diseases of the veins is particularly elucidated by the method with regard to an improvable chronic venous insufficiency and to the differentiation between epifascial and subfascial pathological changes on the venous system. The method is suitable for the differentiation of the possible forms of therapy as well as for the examination of the result of the treatment. By means of this method a judgment of the efficacy of preparations for vein diseases is not possible. At the earliest the technique is comparable with the bloody measurement of the venous pressure-phlebodynamometry. Its smaller exactness should be compensated by triple measurement. The possibilities of errors as well as the advantages of the method and its areas of application preferred are discussed in detail. The light reflexion rheography is nowadays together with the ultrasound Doppler diagnostics a technique of diagnostics which should be present in every phlebologic practice.