This critical review volume explores the theme of ABC transporters in the context of basic cancer research and its role in drug-resistant tumors. The chapters provided complement basic research by including investigations from translational applications to clinical oncology. The development of resistance is a major obstacle in cancer chemotherapy and the field has been moving rapidly in terms of determining the mechanisms for blocking ABC transporter-mediated drug efflux by specific inhibitors and thereby overcoming multidrug resistance. The volume covers these issues in careful detail. Additional topics include the relevance of ABC transporters in resistance to novel and established anticancer drugs and prognosis of patients to compounds, compounds used in photodynamic therapy, tyrosine kinase inhibitors and others. Furthermore, the potential of radiopharmaceuticals for diagnosis of multidrug-resistant tumors and of nanotechnology to combat drug-resistant tumors is also discussed.