In the previous century, apple rootstocks were chosen on the basis of suitability for climate, required degree of vigor, and plant availability. Thus, the rootstock decision in the past was usually quite simple, with only one or two choices available to growers. However, with the proliferation of improved apple rootstocks available around the world, there is now a dizzying array of choices for apple growers. This chapter considers advances in the development and utilization of fruit tree rootstocks using apple as a case study. The history of use of clonal rootstocks is first discussed followed by sections on rootstock improvement efforts, propagation, and evaluation. Rootstock effects on the scion and rootstock tolerance to both abiotic and biotic stress are then considered. The chapter concludes with a discussion on trends in apple rootstock use. Although this chapter focuses mostly on apple, it exemplifies the various inherent rootstock properties and rootstock-induced qualities on grafted scions that can be found in other temperate fruit rootstocks.