Background: Despite continuous research efforts in the past decades, there are still cancers where no effective treatment is available, such as advanced kidney cancer or hormone–refractory prostate cancer. A better understanding of the molecular mechanisms of cancer development and progression is the basis for the development of new diagnostic and therapeutic strategies. Current developments in genomics have a dramatic impact on the whole field of research. The sequence of the entire human genome will soon be fully sequenced and provide the ‘book of life’ as a basis for the understanding of human disease. Methods and Results: New technologies have emerged to translate the human genome sequence into gene function and improved diagnostics or treatment modalities. New technologies such as microarrays are not only important for fundamental research, but will also be useful for diagnostic, prognostic or therapeutic purposes in individual patients. DNA microarrays make it possible to analyze the mRNA expression of thousands of genes simultaneously. The resulting comprehensive gene expression surveys lead to the identification of new genes and pathways with importance in cancer development and progression, or as targets for new therapies. The validation and prioritization of genes emerging from genome screening analyses in large series of clinical tumors has become a new bottleneck in research. Therefore, we have recently developed the tissue microarray (TMA) technology to efficiently test the clinical relevance of candidate genes. TMAs are microscope slides containing samples from hundreds of individual tumor specimens. They can be used for large–scale, massively parallel in situ analysis of genetic alterations on a DNA, RNA and protein level using in situ hybridization or immunohistochemistry on hundreds of tumor specimens at a time. Microarray technologies are already increasingly being used in urologic research, and will also have a strong impact on clinical urology. Conclusions: DNA microarrays and TMAs provide a powerful approach to identify large numbers of new candidate genes, and rapidly validate their clinical impact in large series of human tumors. These technologies will soon lead to a better molecular understanding of urologic tumors, and accelerate the identification of new prognostic markers or therapeutic targets.