Fractionation of yeast nucleic acids (I) by the original or a modified Levene and Jacobs method gave too small yields of cytosylic (II) and uracylic (III) acids to permit conclusions as to primary occurrence of III in I. Preparation of cryst. II and III, the Hg, uranyl, Pb (IV) and brucine (V) salts of II and Pb (VI) and brucine (VII) salts of III are descr.