PURPOSE: Orthostatic proteinuria accounts for the majority of cases of proteinuria that present in childhood or adolescent. This study was conducted to see the prevalence of Nutcracker syndrome (NCS) in children with orthostatic proteinuria using venography. METHODS: Study patients consisted of 23 children with orthostatic proteinuria. The diagnosis of NCS was made by high pressure gradients (> or =4 mmHg) between left renal vein (LRV) and inferior vena cava (IVC) in left renal venography and pressure tracing. RESULTS: Of 23 study patients, the venography showed 12 cases (52%) of typical NCS. Their mean age was 11.5 years (9-14 years). Female predominance (Male:Female=2:10) was noted. In NCS group (n=12), venous pressures of IVC and LRV were 6.50+/-3.34 and 13.21+/-3.53 mmHg, respectively. This pressure gradient between two veins was 6.71+/-2.54 mmHg, which is significantly higher than that of non-NCS group (n=11), 2.17+/-0.94 mmHg (p < 0.05). No positive correlation was observed between urinary protein during 24 hour and pressure gradient (r=0.152, p=0.636). CONCLUSION: NCS may be an important cause of orthostatic proteinuria in children. The prevalence of NCS shown in this study was very similar to that in a doppler sonographic observation published previously. A larger-scale study is necessary to confirm the prevalence.