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. Gene mapping approaches have undergone radical changes in the past decades. In this chapter, we give an overview of these changes emphasizing the importance of the availability of barley reference genomes and sequencing technologies. An overview of the methods and resources for mapping barley genes is given, covering developments over time, and concluding with future trends.