To elucidate whether jaundice of yellowtail is caused by in vivo lipid peroxidation, hemoglobin levels in the blood, 2-thiobarbituric acid reactive substance (TBARS) values, α-tocopherol (α-Toc), ascorbic acid (AsA) and bilirubin levels in the plasma, and heme oxygenase-mRNA (HO-mRNA) levels in the liver of yellowtail Seriola quinqueradiata were analyzed after an intramuscular injection of phenylhydrazine. TBARS values and bilirubin levels in the plasma increased and hemoglobin levels in the blood decreased after the injection. The injection casued hemolysis and hyperbilirubinemia and the fish seemed to demonstrate oxidative stress. Decreases in plasma α-Toc and AsA levels after the injection indicate that these vitamins act as antioxidants to depress in vivo lipid peroxidation. HO-mRNA levels in the liver increased after the injection. These results suggest that oxidative stress caused by the injection leads to the induction of liver heme oxygenase catalyzing bilirubin synthesis and consequently induces hyperbilirubinemia of yellowtail.