Book excerpt: Genomics and Pharmacogenomics in Anticancer Drug Development and Clinical Response provides the most comprehensive body of knowledge available on the role of genetic and genomic variation in the individualization of drug therapies in cancer patients. As a consequence of the intrinsic chromosomal and genetic instability of the tumor genome, it is generally believed that tailoring of chemotherapy in cancer - tients might be achieved by molecular analysis of patient tumor DNA. In addition, to reduce the toxicity risk of patients, the tumor DNA information should be in- grated with the available data on polymorphic drug-metabolizing enzyme and tra- porter genes mediating the exposure of patients to active drugs and/or their active metabolites. The chapters of this book clearly show how DNA information from both the host (germline) and the tumor should be taken into account for rational selection of drug therapies in cancer patients, an aspect that received little attention, despite its importance. The availability of new molecular approaches to the selection of drug therapy is an emerging need, because the traditional approach based on the evaluation of patient and tumor characteristics is clearly far from optimal. Many treated patients do not experience signi?cant bene?ts from the treatment, while they often experience moderate to severe toxicities. In addition, the development and clinical use of novel molecularly targeted agents (alone or in combination with classical cytotoxic therapy) requires the und- standing of the molecular features of the tumors and the identi?cation of tumor markers of response.