This monograph focuses on the clinical use of ultrasound in phlebology. The introduction covers the technical aspects from basic physical principles of the ultrasound signal formation and processing, principles of rheology and the Doppler effect through various ultrasound modalities to practical instructions for setting the ultrasound machine for examination of various areas of the venous system. The next part provides detailed description of the venous anatomy of the lower extremities as a reliable guide for navigating the sometimes variable vein morphology. The core of the book is a description of the principal nosological units in phlebology and methods for their sonographic diagnosis. In the first place is chronic venous disease, along with superficial and deep vein thrombosis, the post-thrombotic syndrome, congenital vascular malformations and variations, and venous aneurysms. The core of the book is the description of the main nosological entities in physiology and the methods for sonographic diagnostics.An increasingly important overlap of ultrasonography from diagnostics to therapy is outlined in chapters on the use of sonography in local venous thrombolysis and surgical treatment of chronic venous disease. The book concludes with several case reports, a practical and a synthesis of all the other chapters, a clinical outllook and a message for everyday practice. Essentially, they are an extract of why the book was created. Increasingly important is the extension of ultrasound diagnostics into therapy, which is outlined in the chapters on the use of sonography for local venous thrombolysis and surgical treatment of chronic venous diseases.