A peptidic fraction having active oxygen scavenging activity was separated from the peptic digest of sardine muscle by ion-exchange chromatography and gel filtration. Further separation by ODS HPLC afforded an active peptide; Leu-Gln-Pro-Gly-Gln-Gly-Gln-Gln. The IC50 value for superoxide scavenging activity was 465 μM as determined by the tetrazolium salt XTT method, while that for hydroxyl radical scavenging activity was 24.6 μM as established by ESR.