Prostate cancer (CaP) mostly occurs in the peripheral zone whereas benign prostatic hypertrophy (BPH) occurs in the transition zone. Human prostates (n=12) were obtained, with ethical approval, from radical retropubic prostatectomies. Following resection, tissue sets consisting of peripheral zone and transition zone were isolated from a lobe pre-operatively identified as negative for CaP. Real-time RT-PCR was employed to quantitatively examine CYP1A1, CYP1A2 and CYP1B1. Quantifiable CYP1A1 expression was observed (in nine out of twelve tissue sets) whilst CYP1A2 mRNA transcripts, although detectable (in six out of twelve tissue sets), were unquantifiable. In ten tissue sets, 2- to 6-fold higher CYP1B1 expression in peripheral zone as compared to transition zone was observed. In the other two, equal CYP1B1 expression levels were observed; retrospective examination identified malignancy in one of the zones. Inter-individual variations (up to 10-fold) in CYP1B1 were also noted. Immunohistochemistry for CYP1B1 showed epithelial and stromal nuclear staining. Since CYP1B1 metabolises hormones and carcinogens our results, if confirmed, suggest that this enzyme may influence susceptibility to CaP.