Previously, we reported that quercetin and resveratrol inhibit the function of androgen receptor (AR). Further studies showed that these two polyphenols caused an increase in expression of c-Jun as well as its phosphorylated form in a dose-dependent manner in prostatic cell lines. Gel shift assay showed that induced c-Jun has specific DNA binding activity. Transient transfections demonstrated that c-Jun repressed prostate-specific antigen promoter activity and transcriptional activity of the AR promoter. These results support a mechanism in which overexpressed c-Jun mediates inhibitory effect on the function of AR. These polyphenols might potentially be useful in prostate cancer prevention.