After a survey of the very extensive literature of the so-called hypernephromas, the writer presents an original study based on embryology of the adrenal and kidney, on the histology of 23 of these tumors, and on experiments as to the effect of fresh tumor extracts on hyperglycemia in rabbits. His conclusions are: anlagal cells of the adrenal cortex are adjacent to metanephros cells in the 16 mm. human embryo, so that embryological inclusion of the former by the latter is by no means improbable; such inclusions could occur also in other tissues, especially those derived from the mesonephros, mesonephric ducts, and genital ridge; the prominent cells of the hypernephromas are similar to those of normal adrenal cortex, not only morphologically, but as regards content of glycogen, fat, lipoid, and lecithin; material is presented in which adrenal cell rest tissue is in close juxtaposition to actively proliferating tumor tissue. Since adrenal cell rests represent the cortical substance of that organ, adrenalin should not be found either in them or in tumors formed from them. Evidence is presented to indicate that these tumors may grow into the walls as well as in the lumen of veins. The writer concludes that his evidence accords with the original view of Grawitz as to the adrenal origin of the hypernephromas.