Prostate cancer is the most frequent malignancy and the second leading cause of cancer deaths among males in the Western world. The clinical course of the disease is highly complex, and genetic factors underlying tumorigenesis are poorly understood. The challenge that lies ahead is to identify the important gene(s) that causes adenocarcinoma of the prostate. Chromosomal findings by cytogenetic and molecular methods, including Southern blotting, microsatellite analysis, fluorescence in situ hybridization, and comparative genomic hybridization, revealed a high frequency of chromosomal aberrations of heterogeneous nature, including: -1, +1, -1q, +4, -6q, -7, +7, -8, -8p, -8q, +i(8q), -9, -9p, -10, +10, +11, -12, -13q, -16, -16q, +16, -17, +17, +17q, -18, +18, -18q, +19p, +20q, +X, -Xq, -Y, and +Y. Specific chromosomal regions of alterations were 1q24-25, 2cen-q31, 5cen-q23.3, 6q14-23.2, 7q22-q31, 8p12-21, 8p22, 8q24-qter, 10q22.1, 10q23-25, 11p11.2, 16q24, 17p13.1, 18q12.2, and Xq11-12. Recently, a predisposing gene for early onset has been localized on 1q42.2-43. The losses of heterozygosity at specific chromosomal loci from chromosomes 5q, 6q, 7q, 8p, 8q, 10q, 13q, 16q, 17p, 17q, and 18q are generally correlated with poor prognosis in advanced tumor stage. In addition, an abnormal function of known tumor suppressor genes from these regions have been observed in prostate cancer. Although, the amplification of the androgen receptor gene at Xq11-13 and HER-2/neu gene at 17q11.2-q12 are novel findings, no single gene has been implicated in harboring prostate cancer. Frequent inactivation of PTEN/MMAC1 tumor suppressor gene at 10q23, MXI-1 at 10q25, KAI-1 at 11p11.2, Rb at 13q14.2, and p53 at 17p13.1 and deregulation of c-myc oncogene at 8q24 have recently been the subject of intense scrutiny and debate.