To study the role of cytochrome P-450 oxidase in menthol biosynthesis of M. piperita, isolation of a gene for cytochrome P-450 oxidase was; attempted. Two specific primers were synthesized from the conserved rigions of cytochrome P-450 oxidase gene of avocado. By PCR amplification of genomic DNA and direct molecular cloning, 423 by long DNA fragment, p2H4, was isolated. Nucleotide sequence analysis of the clone shows an open reading frame encoding 141 amino acids which shows 67 % similarity to that, of cytochrome P-450 from avocado. Southern blot analysis shows that. cytochrome P-450 gene of M. piperita is organised into a multi-gene family, Northern blot analysis shows mRNA size was about 1,800 nucleotides. Southern blot analysis of genomic DNA from other species after PCR amplification shows the presence of similar genes in other plant species.