Cytotoxicity of 4-hydroxy-2E-hexenal (HHE), a hepatotoxic aldehyde, to Chinese hamster lung fibroblast V79 and Balb/c mouse semi-normal cell line BALB/3T3 clone A31 cells was examined. The 50%-inhibitory concentrations to V79 and A31 were 3 μmol/L and 16 μmol/L, respectively. Judging from the sensitivity, HHE might show cytotoxicity below these concentrations. Changes in HHE and malonaldehyde (MA) contents were also examined in yellowtail meat stored at -20°C. HHE content increased up to 60.82±4.39 μmol/kg meat during 28 weeks of storage. In contrast to HHE, MA content increased only slightly in the meat during 28 weeks of storage. From the viewpoint of food hygiene, it is noteworthy that the HHE content increased even when meat was stored at -20°C.