CYP2G1, which is uniquely expressed in the olfactory mucosa of rats and rabbits, may have functions important for the olfactory chemosensory system. The aim of the present study is to determine whether CYP2G genes are present in the human genome. Several gene fragments were obtained by PCR amplification of human genomic DNA. One fragment, termed E7, which contained an open reading frame for 44 amino acids, is highly homologous in deduced amino acid sequence to residues 322-375 in rabbit or rat CYP2G1. Three other gene fragment, termed E7-8, H2Gp1 and H2Gp2, respectively, were also obtained and found to have structural homology with coding sequences in the rat CYP2G1 gene. RNA-PCR analysis of human nasal RNA indicated that at least one CYP2G gene is transcribed. Southern blot analysis of human genomic DNA with use of cloned E7 or E7-8 as the probe indicated that more than one CYP2G-related gene may be present in the human genome. These results provide a basis for further characterization of the structure and function of the human CYP2G genes.