The aim of plant breeding is to create genetically diverse gene pools and then devise strategies to consolidate the favourable alleles and eliminate those that are adverse to the grower’s objectives. Genetic diversity is the fuel that powers plant breeding but it is also the largest impediment to progress. Historically, most cultivar development programmes seem to operate with the assumption that the latter is more important than the former. This chapter describes the major soybean germplasm collections of the world which are the sources of available genetic diversity, then reviews the formation of the current commercially used gene pool for soybean breeding in North America. It then considers how adding new genetic diversity can improve the rate of gain for seed yield and how the various sources of exotic germplasm can be utilized within different segments of a national soybean programme.