The antioxidant potential of chum salmon spermary tissue was evaluated using a sardine triacylglycerol emulsion system. Intact and high-molecular weight water-soluble fractions of spermary tissue were found to accelerate both autoxidation and iron/ascorbate-catalyzed oxidation. The low-molecular weight (LMW) fraction inhibited autoxidation and oxidation catalyzed by iron/ascorbate and 2.2'-azobis(2-amidinopropane) dihydrochloride (AAPH). Inhibition of iron/ascorbate-catalyzed oxidation by the LMW fraction decreased with decreasing pH until no activity was observed at pH less than or equal to 6.4. Activity of the LMW fraction was not strongly influenced by pH (5.0-7.0) in the presence of AAPH. Antioxidants in the LMW fraction, including spermine, putrescine, hypoxanthine, xanthine, and glutathione, both alone and in combination, exhibited less antioxidant activity than the LMW fraction, indicating that other unidentified antioxidants were present.