The matrix metalloproteinases (MMPs) are members of a family of endopeptidases that are able to degrade extra-cellular matrix. MMPs and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs), play a key role in the migration of normal and malignant cell. Interaction of MMPs and TIMPs has been involved in the process of tumor invasion and metastasis. Using cDNA microarray as a screening tool to find androgen regulated gene in prostate cancer, we have found that expression of MMP-13 is regulated by androgen in prostate cancer derived cell line LNCaP. This regulation was further confirmed and quantified by real-time RT-PCR. In addition, the upregulation of MMP-13 mRNA by androgen could be abolished by the androgen antagonist Casodex but not the protein inhibitor cycloheximide. Western blot and immunohistochemistry of MMP-13 confirmed the androgen regulation at the protein level. We have furthermore shown that MMP-13 expression is presented in human prostate cancer obtained from aspiration biopsy. In summary, MMP-13 is androgen regulated and detectable in prostate cancer. Further study of MMP-13 in prostate cancer may help us to understand the progression of the cancer and can lead to new therapeutic options.