About 60 percent of the world’s maize area is planted to high-yielding hybrids (CIMMYT 1994), which are the greatest practical achievement of plant breeding research to date. Another 10 percent of the area, entirely in developing countries, is planted to improved open-pollinated varieties. (The remainder is planted to traditional varieties.) In developed countries, nearly 100 percent of the maize is hybrid. By contrast, in the developing countries, hybrids are planted on about 44 percent of the maize area. Argentina, Brazil, and China account for nearly four-fifths of that. Of the 54 developing countries that grow over 100,000 hectares of maize, only in 15 are improved genotypes regularly planted on over half the maize area (Table 8.1).