The effect of CYP2E1 upon the blood ethanol level was investigated. Blood ethanol concentrations in 4 volunteers whose ADH 2, ADH 3 and ALDH 2 genotypes were identical, were determined after intravenous administrations of 0.20 g/kg of ethanol by gas chromatography. The predicting 95% confidence bounds determined on regression analysis of these data suggested that after venous injection of ethanol, the blood ethanol concentration in a volunteer normal homozygous for CYP2E1 (C1/C1) is higher than that heterozygous (C1/C2). And beta 60 (the blood ethanol concentration-time curve) of the subject heterozygous for CYP2E1 (C1/C2) was higher than that normal homozygous (C1/C1). It is possible that the C2 allele corresponding to the higher CYP2E1 activity may affect the ethanol metabolism.