Rabbits were injected with rat liver nuclei, rat liver ribosomes, the protein from rat liver ribosomes and with soluble ribonucleic acid (sRNA) from yeast, incorporated in Freund's adjuvant. Antibodies measured as hemagglutinins were detected in antisera to ribosomes and sRNA which were specific for nucleotides, nucleosides and bases associated with ribonucleic acid. Hemagglutinins with similar specificities for nucleotides, nucleosides and bases of deoxyribonucleic were found in antisera to nuclei. Antisera to ribosomes, nuclei and ribosomal protein also contained hemagglutinins for ribosomal protein indicating the possible antigenic similarity of the proteins associated with ribo- and deoxyribonucleic acids.