The transcription level of CYP2B1/2 gene in the liver of Sprague-Dawley (SD), Brattleboro (BL) and Wistar (W) rats treated with isosafrol (IS), Arochlor 1254 (AC), phenobarbital (PB) and triphenildioxane (TPD) was studied. The quantity of CYP2B1/2 mRNA was assessed by dot-blot analysis at 18, 48 and 72 hours after inducers administration. The mRNA level in SD and BL rats treated with PB reached its maximum by 18 hours followed by fast decline. For W strain the amount of mRNA reached maximum by 48 hours after treatment. After TPD treatment this parameter for SD, W rats reached maximum by 18 hours, while for BL-72 hours. No differences in the mRNA amount in rats treated with IS and AC were detected. We are not aware of any other data concerning the dynamics of CYP2B1/2 mRNA accumulation during IS-induction. We showed that in this case a maximum of mRNA was reached by 18 hours. Thus, we revealed inducer- and strain-dependent of differences in mRNA accumulation dynamics.