Maize, a thermophilic plant species, originates from subtropical highlands. Maize cultivation, however, has spread to temperate regions of the world that experience low temperatures during the early development of the plants. Maize genotypes that are cultivated in cooler climates need to have a short vegetation period and the ability to adapt to low temperatures. By growing cold-tolerant hybrids it is possible to achieve improvements in stand uniformity, the rate of plant development and the yield. In addition, cold-tolerant hybrids can be sown earlier, making it possible to grow hybrids with longer vegetation periods and greater yield potential. This chapter will discuss the physiological and genetic background of cold tolerance, the methodology required for its analysis, ways of improving cold tolerance by breeding, and the seed production aspects of this trait.