The androgen receptor gene (AR) plays an important role in molecular signaling and regulation and the subsequent cellular growth of prostate cancer. In addition, it is a highly variable region of the genome. We used direct nucleotide sequencing to genotype the entire exogenous coding region of the androgen receptor in ten commonly used prostate cancer cell lines. Our analysis confirmed the presence or absence of several known SNPs in the cell lines studied. We also assayed the number of CAG-repeat and GGC-repeat sequences for each for the ten cell lines. Our analysis identified three new mutations, one each in the DU145, LnCAP and RWPE-2 cell lines. In DU145, the DNA isolated in our lab was heterozygous at G527G (T>C transition), a polymorphism not previously reported. The LnCAP cells cultured in our lab were found to have a T>C transition (heterozygous), resulting in a S641P change that was not present in the ATCC cell line DNA. Lastly, a homozygous G>T transversion was found in RWPE-2 cells, resulting in the S187I change. This is potentially significant for use in cell culture and future cell model development.