We report the clinical and pathologic findings of 2 siblings affected with congenital nephrotic syndrome (CNS). The parents were a nonconsanguineous Mexican couple. The first sibling was born at term and developed proteinuria, hypoproteinemia, edema and ascites by its second month of life; he died septic at 6 months of age. The second sibling was diagnosed with congenital nephrosis during the second trimester of pregnancy. Prenatal demonstration of reno-placentomegaly can help in making the presumptive diagnosis of CNS in patients with high maternal serum and amniotic fluid AFP, normal acetylcholinesterase and normal karyotype. The pathologic findings of the kidneys of these siblings demonstrate that tubular microcysts are not critical to the disease process and are only the manifestation of a progressive disease in which the primary renal defect probably resides in a lack of integrity of the glomerular epithelial cells serving as filter.