1) The purification procedures of a ribonuclease [EC 2.7. 7.17] from Rhizopus sp. were revised. The yield of the crystalline enzyme was about 35%. The crystalline enzyme was shown to be homogeneous by gel electrophoresis and ultracentrifugation. 2) The molecular weight of the ribonuclease was estimated to be ca. 24, 000 by means of gel filtration on Sephadex G-75. 3) The amino-terminal amino acid of the enzyme was determined to be glycine. 4) The amino acid composition of the RNase was determined. 5) The CD spectrum and ORD of the enzyme were measured in an aqueous solution and in 8 m urea.