The embryonal renal neoplasms occurring in infancy and childhood constitute a heterogeneous but closely related group of tumors. Histologically and histogenetically they are not identical. All intermediate varieties are found, from the type containing muscle fibers, described by Cohnheim,1 to a tumor which is mostly glandular. In 1828, Gairdner2 presented the first case report of a renal sarcoma occurring in infancy. Eberth3 first accurately described this tumor in 1872. Other authors whose names are associated with the discovery and early descriptions of this disease are Cohnheim4 in 1875, Sturm5 in 1875, Weigert6 in 1876, Landsberger in 1877, Osler7 in 1879, Huber-Bostroem8 in 1879, Brosin9 in 1884, Paul10 in 1886, and Doederlein11 in 1894. In 1899, Wilms12 wrote his classic monograph on mixed tumors of the kidney. This neoplasm has since borne the eponym of "Wilms tumor." The term