To clarify the key peptides that account for the cooked taste of puffer fish, this study examined flavor peptides extracted from the flesh of puffer fish (Takifugu obscurus).Peptides fractions(P1, P2, P3, P4 and P5) were purified from an aqueous extract of Takifugu obscurus muscle by ultrafiltration, and Sephadex G-15 gel filtration chromatography (GFC).Fraction P2 was identified as having the greatest intensity of umami and sweet taste by sensory evaluation analysis and by electronic tongue determination.P2 was further fractionated into P2a, P2b, P2c by reverse phase high performance liquid chromatography (RP-HPLC).Fraction P2b contained peptides at relatively high concentration,which unlike P2a and P2c, elicited desirable taste properties, such as umami and sweet taste as found in the cooked flesh muscle of Takifugu obscurus.The amino acid sequence of P2b subfraction was identified as Tyr-Gly-Gly-Thr-Pro-Pro-Phe-Val (836.4 Da) by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF/TOF MS/MS).Hydrophilic amino acids residues Tyr,Gly, Gly, Thr, Phe are likely to contribute to the sweet and umami taste of this octapeptide.Further investigation was conducted to evaluate the taste properties of this octapeptide by the electronic tongue.Principal component analysis (PCA) suggested that sucrose and monosodium glutamate (MSG) enhanced the umami taste ofP2b subfraction.However, sodium chloride (NaCl) and citric acid had a small effect on the taste of P2b.This may indicate that there were synergistic effects of sucrose and monosodium glutamate (MSG) on this octapeptide.The results of this study also suggest that peptides are important components of the mellowness and tenderness taste of the Takifugu obscurus.