The association of nephrotic syndrome and renal vein thrombosis has been increasingly reported in the literature due to the use of modern complementary explorative techniques. The incidence of renal vein thrombosis in the nephrotic syndrome varies according to the different authors. The pathogenesis of this association has been widely discussed and even though renal vein thrombosis has formerly been considered as one more cause of nephrotic syndrome, there are at present numerous arguments supporting the opposite thesis. A case of nephrotic syndrome and unilateral thrombosis of the renal vein in a patient with primitive extramembranous glomerulonephritis is reported. Blood coagulation studies revealed an initial hyperfibrinogenemia and a persistent decrease of factors V, VII, and X, with low rates of prothrombin. A thrombectomy was carried out, but the patient presented a Gram-negative sepsis without hypotension in the immediate postoperative period. As a consequence an acute renal failure developed and hemodyalisis was necessary for 2 months. The pathogenesis of both conditions are discussed.