Volatile compounds collected by simultaneous distillation and extraction under reduced pressure from fresh and stored (10°C, 24h) sardine Sardinops melanosticta mince were analyzed by GC/MS. According to the lowering of freshness in sardine, a total of 39 carbonyls (carbon numbers 5-15, C_5-15) and alcohols (C_2-8) increased, especially 2, 4-heptadienal, 3, 5-octadiene-2-one, 2, 4-decadienal, and 2, 4, 7-decatrienal. The presence of fishy odor compounds (E, E, Z)-2, 4, 7-decatrienal and (E, E, Z)-2, 4, 7-tridecatrienal in the volatiles was established by synthesis of authentic compounds. This finding suggested that C_7-13 carbonyls formed via autoxidation of PUFA, such as 2, 4-heptadienal, 3, 5-octadiene-2-one, 2, 4-decadienal, 2, 4, 7-decatrienal, and 2, 4, 7-tridecatrienal are the main contributors to the characteristic fishy off-flavor of sardine.