Nucleotide composition of the sum total DNA of B. bifidum, biotype III, was determined by paper chromatography in combination with ultraviolet spectrophotometry. DNA of B. bifidum was referred to the GC-type (GC -- 62.6 mol%). Two additional nitrogen bases were present in the DNA composition; 5-methylcytosine and 6-methylaminopurine -- 0.45 mol% and 0.20 mol%, respectively. Nucleotide composition of the sum total RNA was studied with the aid of high-voltage electrophoresis in combination with ultraviolet spectrophotometry. The sum total RNA was referred to the high GC-type (GC -- 64.9 mol%). These data permit to consider it reasonable to refer bifidobacteria to the Bifidobacterium genus.