The cDNA encoding the mouse Cyp2e1 protein has been isolated and sequenced, and shown to share 92%, 79%, 80% and 79% sequence similarity over the coding region with rat, human, rabbit 1 and rabbit 2 CYP2E1 cDNA sequences respectively. The predicted Cyp2e1 protein contains 493 amino acids, with a molecular mass of 56781 Da. The protein contains many features common to other cytochrome P450s, including a potentially phosphorylatable serine residue at position 129 within a canonical cyclic AMP-dependent protein kinase site. Southern blot analysis of genomic DNA prepared from C57BL/6 and DBA/2N mice suggests the presence of only a single Cyp2e1 gene. The Cyp2e1 gene was isolated and its organization was established by PCR using oligonucleotides to its predicted intron/exon boundaries. These results showed that the mouse Cyp2e1 gene is approx. 11,000 bp in length and has a similar structure to the human and rat CYP2E1 genes. Cyp2e1 protein expression was studied in a variety of tissues and a sexual dimorphism in its levels in some tissues was noted. Acetone treatment induced the Cyp2e1 protein in all of the tissues studied in both sexes, but this Cyp2e1 protein induction was not accompanied by an increase in Cyp2e1 mRNA levels. Indeed, mRNA levels were seen to be decreased on treatment, suggesting that acetone administration affects either mRNA translation efficiency or protein stability. Of a wide range of drugs known to modify other cytochrome P450 levels only diethylnitrosamine had a significant effect on Cyp2e1, causing a decrease in protein levels.