The human CYP17 gene, located on chromosome 10q24.3, plays a key role in sex steroid synthesis, mainlyrelated to estrogen. A 5’ UTR polymorphism involving a single base pair change in the promoter region resultsin increased transcriptional activity. In the present study of 250 breast cancer cases and 250 ma tched controls,the A1 genotype frequency was elevated in the disease group, while the A2 genotype frequency demonstratedno association. When data were stratified by risk conferring group, however, the A2 genotype frequency wasincreased in postmenopausal breast cancer cases (4.2%), patients positive for a family history of breast cancer(5.5%), high BMI, estrogen receptor (6.2%) and progesterone receptor negative (5.0%) status, HER2/neupositive (7.7%) status, positive node status (5.0%) as well as advanced stage of the disease. The A1A1 genotypelinked with increased production of androgens might impact on onset of breast cancer while the A2 allele showedassociations with respect to important risk conferring parameters.