PURPOSE: To evaluate the usefulness of Doppler US in the diagnosis of nutcracker syndrome. MATERIALS AND METHODS: This study included twenty-nine patients who were clinically suspected to have nutcracker syndrome and subsequently prospectively underwent Doppler US and left renal venography. On Doppler US, peak velocity (PV) of the aortomesenteric (AM) portion and the hilar portion of the left renal vein (LRV) was measured, and the ratio of peak velocity (AM to hilar portion of LRV) more than 5.0 was considered as a Doppler criteria of nutcracker syndrome. The diagnosis of nutcracker syndrome was confirmed at left renal venography by demonstrating the pressure gradient more than 3 mmHg between inferior vena cava (IVC) and LRV. The findings of Doppler US were compared with those of left renal venography. RESULTS: Among twenty-three patients who showed PV ratio more than 5.0, the pressure gradient between IVC ad LRV was more than 3mmHg in twenty patients and less than 3 mmHg in three. Among six patients who showed PV ratio less than 5.0, the pressure gradient between IVC and LRV was more than 3 mmHg in the two patients and less than 3 mmHg in four. According to the results of Doppler ultrasonography compared with those of left renal venograpy, the sensitivity, specificity, postive predictive value, negative predictive value and accuracy in the diagnosis of nutcracker syndrome were 91 %, 57 %, 87 %, 33 % and 83 %, respectively. CONCLUSION: Doppler US may be a useful screening test in the diagnosis of nutcracker syndrome, considering its high sensitivity and low specificity.