Pharmacogenetics in oncology will ideally allow oncologists to individualise therapy based on a genetic test result. Severe toxicity and clinically significant underdosing may be avoided, whereas predicted non-responders can be offered alternative therapy. This manuscript gives an overview of heritable variants in the genes of nine enzymes or pathways that have been studied most extensively in anticancer chemotherapy. Even though many pharmacogenetic association studies have been published, there is a need for more research. In particular, there is a need for replication of data and development of predictive models. Prospective trials are required to establish clinical value and cost-effectiveness of pharmacogenetic testing in oncology.