Bilateral nephromegaly with a histological picture of diffuse Wilms' tumor or so-called bilateral nephroblastomatosis is a rare condition. We present an additional case documented by urography. To our knowledge, this is the first report of diffuse nephroblastomatosis recognized at 2 hours of age. A few cases are reported but urographic documentation is available in only 4 of those and in our own. The review of the urographic findings reveals features which seem seem to be nearly pathognomonic of this condition. Urographic appearance similar to that of adult type polycystic disease without the typical radiolucent cysts, should raise the suspicion of a diffuse bilateral process in the kidneys. Exclusion of other infiltrative diseases, like leukemia and glycogen storage disease, should lead to radiologic diagnosis of nephroblastomatosis. Renal biopsy is then indicated.