Cancer chemotherapy shows nonspecificity, narrow therapeutic indices, severe toxicity, unpredictable efficacy, and heterogeneity in their therapeutic and toxic responses across patient populations. Pharmacogenomics endeavors to elucidate the effect of genetic inheritance on the individual variation of drug response and toxicity. Many genetic factors such as genetic polymorphism in drug metabolism enzymes, drug targets, drug transporters and etc. are much responsible for variable responses and tolerability of cancer chemotherapy. Pharmacogenomics has therefore great potential to improve cancer treatment outcomes by either reducing toxicity or increasing efficacy, with its ultimate goal of realizing individualized optimal cancer chemotherapy or tailored drug therapy based upon the genetic profiles of each individual in clinical filed. Clinically relevant pharmacogenomic examples of anti-cancer drugs in their metabolism, transporters and targets are discussed. Other topics briefly discussed also in this article include the role of pharmacogenomics in the development of new anti-cancer drugs, ethical issues raised in pharmacogenomic studies, and educational needs of pharmacogenomics-related knowledge in the undergraduate, postgraduate, and continuing medical education courses.