The purification of RNase C2 from 76.5 1 of Asp. clavatus cultural fluid and RNase Pch1 from 160 1 of Pen. chrysogenum 152 A cultural fluid was described. 1150-fold purification of RNase C2 was attained by precipitation with ammonium sulfate, ion-exchange chromatography and rechromatography on DEAE-cellulose, gel chromatography on Sephadex G-75, and crystallization from diluted acidic buffer. During the preparation of RNase Pch1 additional chromatography on CM-cellulose was used before crystallization, the purification being 2220-fold. It was obtained 600 mg RNase C2 and 900 mg RNase Pch1. Some physico-chemical properties of crystalline RNases were studied.