In order to screen the genes differentially expressed in two human prostate cancer cells with different metastasis potentials, suppression subtractive hybridization (SSH) was done twice on human prostate cancer cell line with high potential of metastasis PC3M-1E8 and its synogenetic cell line PC3M-2B4 with low metastasis potential. In the first subtraction PC3M-2B4 was used as tester and PC3M-1E8 as driver and the forward subtractive library was constructed. In the second one the tester and driver were interchanged and the reverse subtractive library was constructed. The screened clones of both libraries were sequenced and Gene Bank homology search was performed. Some clones were confirmed by quantitative real-time PCR. The results showed that two subtrac-tive libraries containing 238 positive clones were constructed. Analysis of 16 sequenced clones ran-domly picked from two libraries showed that 4 differentially expressed gene fragments were identi-fied as new EST with unknown functions. It was concluded that two subtractive libraries of human prostate cancer cell lines with different metastasis potentials were constructed successfully.