Barley is the fourth most cultivated cereal in the world and is thus an important crop in breeding. A large variety of traits are needed for resistance to various stresses as well as to meet the requirements of its several uses. To breed efficiently for those traits, identification of the causal genes and availability of genetic markers for selection are important targets for research. This chapter offers an overview of recent changes in this field, emphasizing the importance of the availability of barley reference genomes and sequencing technologies. The chapter outlines the methods and resources for mapping barley genes, covering developments over time and presenting a detailed case study. Finally, the chapter looks ahead to future research trends in this area and offers guidance on further reading.