Carassius awratus was chosen as the experimental materials to study the dynamic effects of 1 mg/L 2-nitro4'-hydroxydi-phenylamine on the induction of HSP70 in the fish livers and brains.Using the SDS-PAGE and Western Blotting techniques, the expression level of HSP70 in the fish livers and brains was evaluated.As shown from the results, 2-nitro-4'-hydroxydiphenylamine treatment resulted in a time-dependent elevation in HSP70 expression at 2, 4, 7, 10 and 16 days exposure.Comparing with the control group,the HSP70 in the fish brains and livers began to express significantly after being exposed for4 days and 7 days respectively.The expression level of HSP70 was enhanced with the exposure days increasing and showed a good time-effect relationship.Results from this study suggest that HSP70 as an environ menial biomarker can be a sensitive and rapid indicator in the aquatic ecosystem.