The production of genetically homozygous inbred lines is essential for hybrid maize breeding. There is a strong interest in the use of DH lines in research and maize breeding due to their many advantages compared to inbred lines produced by the traditional method of recurrent selfing. This chapter describes the major steps in production of DH lines in maize and present current research, from the production of haploid seed to the harvest of DH seed. The chapter reviews recent findings concerning the genetics behind haploid induction and new and more efficient methods for identification of haploids. The chapter discusses chromosome doubling protocols as well as recent research on spontaneous chromosome doubling, which may have the potential to make DH production more efficient. Finally, the chapter considers practical aspects of the cultivation of plants derived from haploid seeds as well as applications and advantages of DH lines in maize breeding, and provides detailed guidance on further reading in this area.