Methamphetamine is one of the most popular recreational drugs in Central Europe and is often combined with ethanol. Various interactions between these two substances have been described including the influence of administered ethanol on biotransformation of methamphetamine. The aim of the present study was to describe the opposite effect - the influence of methamphetamine on biotransformation of ethanol in rats. Methamphetamine was administered for 10 days (10 mg/kg/day) i.p. and ethanol was delivered as an intragastric bolus (2 g/kg) on the10th day of experiment to both methamphetamine administered rats and control animals. The pharmacokinetic experiment on the whole animal was performed and plasma samples were drawn at the 40th, 120th, 210th and 300th minute after ethanol administration. Ethanol plasmatic levels reached significantly lower values in the 40th and 120th interval when compared to controls. Differences were insignificant in the last two intervals. Our results suggest that chronic methamphetamine administration induces ethanol biotransformation. We suppose that this effect is caused by induction of alcohol dehydrogenase metabolic activity or by allosteric interaction of methamphetamine and this enzyme. More studies have to be conducted to confirm or disprove our hypothesis.