The ability of a motif of the CYP17 5' untranslated region, created by a polymorphic T to C substitution, to bind to the human transcription factor Sp-1 was investigated. No binding of any of the polymorphic alleles was observed in electromobility shift assay. No other sequence within +1 to +100 of each of the CYP17 alleles formed complex with the Sp-1 or enhanced binding to the polymorphic CACC box. Genotyping of 510 breast cancer patients and 201 controls revealed no difference in genotype frequencies. Age at onset, tumor grade, lymph node status and distant metastases, stage, and estrogen and progesterone receptor status were not associated with the CYP17 genotype.