Cytochromes P450 (P450) are a superfamily of membrane-bound hemoproteins that oxidize a large number of endogenous and exogenous compounds. The recently cloned P450 gene (CYP1A5) encodes the primary protein responsible for epoxidation of aflatoxin B1 (AFB1) in the turkey, an animal extremely sensitive to this mycotoxin. Hypersensitivity of turkeys to AFB1 was first demonstrated by association with 'Turkey X Disease' which caused widespread deaths of turkeys and other poultry throughout Europe in the 1960s, later shown to be caused by AFB1-contaminated feed. In this study, comparative genomic approaches were used to selectively amplify and sequence the introns and 3′ flanking region of CYP1A5. The structure of the CYP1A5 gene in the turkey is shown to be equivalent to that of the human CYP1A genes with seven exons of 38, 858, 127, 90, 124, 87 and 307 bp, respectively, and six introns. A single nucleotide polymorphism (SNP) in the 3′ UTR was used to assign CYP1A5 to turkey linkage group M16 (equivalent to chicken chromosome 10). The results of this study provide the framework for identifying allelic variants of this biochemically important P450 gene in poultry.