The typical symptoms of the deep phlebothrombosis are not always given, often we have to do with a quiescent or atypical form of the course. For this reason not only the classical symptoms but also the differential-diagnostic considerations were mentioned. Apart from the clinical examination the ultrasound Doppler sound and above all the phlebography will help us for finding the diagnosis. As to the therapy in particular the thrombolytic treatment is discussed. Hereby nowadays the so-called ultrahigh streptokinase treatment seems to preponderatell, since it also develops a shortening of the time of therapy, the conventional lysis with urokinase is reserved to the risk patients. Not only the immediate results as well as the long-term results concerning the formation of a postthrombotic syndrome are mentioned.