The rodent testis is generally more susceptible to cadmium(Cd)-induced toxicity than the liver. In order to clarify the molecular mechanism of Cd-induced toxicity in testis, Cd-induced metallothionein(MT) gene expression and MT protein accumulation under different time in testis and liver were compared. MT1 and MT2 mRNA levels were determined by reverse transcription-PCR analysis followed by densitometry scanning, and MT was quantitated by the ELISA method. Both MT mRNA and MT were constitutively present in testis as well as the liver. Testis had higher levels of MT1 and MT2 mRNAs in 1 h, 3 h, 6 h and 24 h over control, but MT protein did not increase. Cd exposure increased hepatic MTs mRNA and MT protein. Thus, it is indicate that, although Cd exposure results in increases of MT mRNA in testis, it does not enhance MT synthesis. The inability to induce the metal-detoxicating MT-protein in response to Cd, might account for higher susceptibility of testis to Cd toxicity and carcinogenesis relative to liver.