Dialysis, gel-chromatography on Sephadex G-75 (superfine) and chromatography on sulphoethylcellulose give high yield (68 per cent) of 162-fold purified ribonuclease from cobra venom. In ion-exchange chromatography, ribonuclease is eluted in two fractions. The fraction with the highest specific activity has a molecular weight of 15900 and is homogeneous in 15 per cent polyacrilamide gel electrophoresis at pH 8.9. Electrophoresis at pH 4.3 reveals a minor fast component of this fraction which also exhibits a ribonuclease activity. Sulphoethylcellulose chromatography fairly separates cobra venom phosphodiesterase and 5'-nucleotidase eluted as a single fraction in gel chromatography.