Metallothionein (MT) is a metalloprotein with high affinity for certain heavy metals. In the present study, the ability of cadmium (Cd) to induce the synthesis of MT in dental pulp was investigated. Rats were injected subcutaneously with CdCl2 (1.5 mg Cd/kg) daily for 7 days. Expression of the MT gene was demonstrated by reverse transcription polymerase chain-reaction techniques. The results indicate that Cd induced MT in dental pulp of rat incisor and this may be involved in the cellular defense mechanism against Cd toxicity.