The results of comprehensive study of vitamins during the last two decades are reflected in the more efficient methods being used at present for the control of deficiency diseases. The final word may not have been said in respect to rickets, but the investigations of Tanret, Rosenheim and Webster, Hess and Windaus, and Steenbock on the production and action of vitamin D has contributed materially to our knowledge of the etiology, prophylaxis and treatment of the disease. The process of imparting the antirachitic factor to sterols by ultraviolet emanations from a mercury vapor lamp is too familiar to need elaboration in this report. The name viosterol was assigned by the Council on Pharmacy and Chemistry of the American Medical Association to irradiated ergosterol when adjusted to a potency of 100 times the vitamin D strength of standardized cod liver oil. Since Oct. 1, 1930, the strength of these preparations has