Twenty-six adult patients with idiopathic nephrotic syndrome, ages ranging from 16 to 62 years, were prospectively evaluated with selective renal venogram for the presence of renal vein thrombosis (RVT). Ten patients had membranoproliferative glomerulonephritis (MPGN); 5, membranous nephropathy (MGN); 3, diffuse proliferative glomerulonephritis (DGPG), and 1 focal glomerulonephritis (FPG). Renal vein thrombosis was observed in 11 patients. The primary nephropathies in these patients were: MPGN in 4, MGN in 3, FGS in 2, FPG in 1, and DGPG in 1. All patients were asymptomatic. The clinical and renal pathology features were similar in patients with and without RVT. Other thromboembolic complications were observed in 4 patients. In conclusion, renal vein thrombosis was observed in 42% of our patients and MPGN was the most frequent nephropathy associated with RVT.