In U.S.A. maize breeding, exotic germplasm is considered as high-risk and usually introduced by backcrossing specific traits into elite lines. The U.S.A. maize germplasm base is narrow. Only a few open-pollinated varieties are well represented in current programs. Currently, the barrier in using of exotic germplasm in the U.S.A is less formidable than in the 1980s. The major reason is that U.S.A materials are now used in tropical breeding to accelerate earlier maturity and lodging resistance. These exotic materials, developed with U.S.A germplasm, are being introduced back into the U.S.A.Since1994, the ARS-led Germplasm Enhancement of Maize (GEM) project has sought to help broaden the genetic base of America’s corn crop by promising exotic germplasm and crossing it with domestic lines. New hybrids derived from such crosses have provided corn researchers and the producers. These may include improved or alternative native source of resistance to insect pests such as corn rootworms and diseases like northern leaf blight. GEM’s aim is to provide source of useful genetic maize diversity to help the producers to reduce risks from new or evolving insect and disease threats or changes in the environment or respond to new marketing opportunities and demand. During the 2009 growing season, the Ames (Iowa) and Raleigh (North Carolina) locations managed or coordinated evaluations on 17,200 nursery plots as well as 14,000 yield trial plots in Ames and 12,000 in Raleigh. A new “allelicdiversity” study is devoted to exploring and capturing the genetic variation represented by over 300 exotic corn races. Since 2001, GEM has released 221 new corn lines to cooperators for further development into elite commercial new hybrids. GEM has already identified about 50%-tropical, 50%-temperate families tracing primarily to tropical hybrids that are competitive with commercial checks. In North Carolina State University program, they have examined the potential of tropical inbredand hybrids for U.S.A. breeding by crossing temperate-adapted, 100%-tropical lines to U.S.A hybrids. There should be favorably unique alleles or genomic regions in temperate germplasm that can be helpful in tropical maize improvement as well as utilization of tropical lines in temperate areas.