OBJECTIVE To study the changes in the matrix metalloproteinases-2 and 9 (MMP2, MMP9) induced by 60Co y-ray extal irradiation of human prostate cancer PC-3 cells.METHODS Human prostate cancer PC-3 cells were irradiated with different doses of 60Coy-rays. Cell migration and invasiveness were evaluated and the expression of MMP2, and MMP9 was investigated by RT-PCR, West blotting and flow cytometry(FCM).RESULTS Irradiation enchances invasive protential at the doses of 1,3 and 5 Gy.whereas it significantly inhibits cell migration. CONCLUSION The different doses of 60Co y-ray extal irradiation for prostate cancer may have different effects through the changes of MMP2, and MMP9 expression.