BACKGROUND: Venous thrombosis is a multicausal disease involving intravenous clot formation. It may occur spontaneously or after provoking events, such as traumatic injuries to the pelvis, upper and lower extermities, immobilization, intravascular procedures, including venous catheterization or injection. Color Doppler ultrasonography is a rapid and non-invasive technique for evaluation of venous disease. It is a very sensitive method for detection of thrombi, but has some limitations, e.g. inability to distinguish between an old and fresh thrombus. Elastography as a method for evaluation of tissue elasticity and allows more accurate assessment of venous thombosis. The thrombus solidifies significantly during the process of remodeling, thereby changing elasticity, while the tissues located around the vessel remain unchanged. Moreover, the homogeneity of the thrombus is also changed. These factors allow for exact determination of the age of the thrombus depending on changes of its elasticity. MATERIAL AND METHODS: The object of this study was to assess thrombus age in patients with saphenous vein insufficiency treated with sclerotherapy. We examined 34 patients, 30 women and 4 men, aged 18-62 years. All short-listed patients with initial 7-8 mm vessel diameter underwent treatment with 3% Aetoxysklerol mixed with CO2 and other respiratory gases. Data acquisition was performed using an Esaote MyLab Twice device with LA523 linear probe. RESULTS: On the sixth day after the treatment 31 patients presented uniform, hypoechogenic thrombus in B-mode image. Ultrasound-based elasticity images (elastography) showed significant predominant red and green areas. Blue area was either invisible or appeared in insignificant grade on examined area. The mosaic image of colors appeared on 2 patients. On the fourteenth day of study 21 patients still presented hypoechogenic thrombus, whereas mixed echogenicity of thrombus appeared on 11 patients. On 28 examined patients mosaics of red, green and blue colors were observed, with blue color significantly predominating over red color. 3 patients presented mosaics of colors without a predominate color. CONCLUSIONS: Elastography as a method of thrombus evaluation, provides information about relative shrinkage of blood clot. It seems that elasatography can improve accurate assessment of the exact age of thrombus.