We measured serum aldolase levels in Yusho sufferers annually between the years 2000 and 2005. We observed a decrease in serum aldolase levels in 47.7% of the patients studied. We researched the relations among serum aldolase, serum creatine kinase, blood polychlorinated biphenyls, blood polychlorinated quaterphenyls, blood polychlorinated dibenzofurans and toxic equivalent quantity statistically. We conclude that a high concentration of blood polychlorinated biphenyls might play a role in the decrease of serum aldolase levels in Yusho sufferers.