Among all participants and post-menopausal participants only, carriers of at least one CYP1B1 453Ser allele had a borderline statistically significant increase in the risk of developing breast cancer compared to women carrying the referent Asn/Asn genotype (all participants: OR 1.48, 95% CI 0.95, 2.32; post-menopausal participants: OR 1.61; 95% CI 0.94, 2.74). Here, CYP1B1 is linked to breast cancer.