The amino acid sequence of ribonuclease F1 reported earlier (Hirabayashi and Yoshida (1983) Biochem. Int. 7, 255-262) was revised. The revision was an interchange between residue 32 (Ser) and residue 36 (Thr). Thus, the correct sequence from residue 32 to 36 is -Thr-Ala-Gly-Ser-Ser-. The error in the original sequence had been pointed out by X-ray crystallography (Vassylyev et al. (1993) J. Mol. Biol. 230, 979-996) and confirmed chemically in the present study.