 Outpatients symptomatic for suspected DVT of a leg are examined by a vascular doctor according to standard procedure based on pre-test clinical probability PTCP assessment, D-dimer assay and a CUS limited to the proximal deep veins. Those in whom a proximal DVT is excluded and have intermediatehigh PTCP or altered D-dimer level are eligible for the study. The included patients are immediately submitted to an extensive echo-color-Doppler examination of calf deep veins by a different vascular doctor and results are closed in an envelope that will be open after three months or before if necessary. In the meantime, patients will follow the standard diagnostic procedure: they receive an appointment to come back in 5-7 days for a further CUS examination, or even before in case of worsening of symptomssigns. All the included patients receive a telephone call after three months to exclude possible complications. 