Molecular genetic alterations characterize the development of human cancer. Recent advances in molecular genetic technology and the success of the human genome project have empowered investigators with new tools in dissecting the cancer genome for discovery of new cancer-associated genes. The purpose of this review is to highlight the emerging molecular genetic methodologies and summarize their principles, applications, and potential technical challenges. The critical issue in sample preparation and a strategy that combines different molecular techniques to facilitate the identification of novel cancer-associated genes will be discussed. As compared with conventional cytogenetics methods, digital karyotyping, array comparative genomic hybridization, and representational oligonucleotide microarray analysis provide an unprecedented mapping resolution that allows a precise localization of the amplified and deleted chromosomal regions. These technologies can be combined with gene expression profiling and high-throughput mutational analysis to facilitate the search for new cancer-associated genes. It is expected that applying these new technologies will lead to discovery of a host of novel oncogenes and tumor suppressors, which will have a significant impact in our understanding of tumorigenesis and in the clinical management of cancer patients.