Publisher Summary The development and progression of cancer is associated with the alterations of genes that control growth and differentiation. The accumulation of genetic changes—such as inactivation of tumor suppressor genes—and the alteration of function of oncogenes, growth factors and their receptors, and genes related to metastatic growth characterize the multistep nature of tumor development. Renal cell carcinoma is the most common malignant tumor arising from the kidney. The cytogenetic analysis, especially in combination with DNA analysis, is a powerful technique to detect new tumor-associated genetic alterations. Molecular cytogenic methods are efficient to stratify renal cell tumors. This chapter emphasizes on the complexity of genetic alterations in the subtypes of renal cell tumors and indicates that specific genetic changes are useful in the diagnosis as well as in the separation of high-risk groups for therapy. The genetics of nonpapillary renal cell carcinomas include sporadic and familial renal cell carcinomas. The genetics of papillary renal cell tumors is also discussed in the chapter. A model of nonhomologous mitotic recombination in renal cell carcinomas is diagrammatically represented in the chapter. The renal oncocytoma and chromophobe renal cell carcinoma are also discussed in the chpater.