Purpose: To evaluate the sensitivity and specificity of the method for determining the clinical class of chronic venous diseases using the Ivenus application (within C0-C2 according to CEAP). Materials and methods: Patients who applied to several phlebology clinics for an initial consultation are consistently included in a multicenter prospective study. At the appointment, a doctor with at least 5 years of experience takes photographs of the lower extremities and uploads them to the IVENUS application, which automatically determines the clinical class according to CEAP, without showing the results to the surgeon (blinding). Further, the doctor independently determines the clinical class according to CEAP and enters the data into the register. The object of the study is a photograph of a certain area of the lower limb.