Recent advance of radiographic technique makes antemortem diagnosis of renal vein thrombosis (RVT) possible. However the incidence of RVT in patients with nephrotic syndrome(NS) is still not known. This study was designed to investigate the incidence, clinical presentation and radiological features of RVT in NS patients in China. A prospective study including clinical, and pathological examination as well as renal venogram was carried out in all our hospitalized NS patients except those having contradiction for renal venogram. RVT was found in 23 of the 54 cases (42%) and there was obstruction in 34 renal vein branches. RVT was more common in left (19) than right side (15), in upper (19) than middle and lower branches (10). It is interesting that in our group not only membranous but also minimal change as well as mesangium proliferative glomerulonephritis had high incidence of RVT (47%, 45% and 36% respectively) Only 6 cases (26%) had a typical acute presentation with severe loin pain, significant increase of urinary protein, enlargement of involved kidney. Occasionally fever, deterioration of renal function and sterile urinary white cells were also present. The remaining patients (74%) had latent onset of RVT which could hardly be identified in the clinical course of the underlying NS. For the high incidence and atypical clinical course of RVT shown in our study, it is recommended that due attention should be paid of this complication during management of NS and interpretation of therapeutic response.