To the Editor.— Doctors Fraley and Najarian ( 212 :1377, 1970) report a case of renal vein thrombosis in a newborn. There are no other neonatal conditions in which a mass in the flank region, hematuria, thrombocytopenia, anemia and nonvisualization on intravenous pyelogram occur, which regress, other than renal vein thrombosis. It is true that the conservatives will not call their surgical colleagues to do a biopsy in a disease they feel should be managed medically. Our successful outcomes are, therefore, clinical. The English surgeons feel that renal vein thrombosis is a medical disease. No one argues that a delayed nephrectomy may be needed for a chronically infected or atrophic kidney. We have recently reported ( Clin Pediat , to be published) a newborn infant with bilateral renal vein thrombosis and inferior vena cava thrombosis. In the acute state, there were bilateral expanding masses in the flank region, hematuria, thrombocytopenia, and anemia. X-ray