The use of high-yielding varieties (HYV’s) of wheat and rice has expanded sharply in the developing nations in recent years. This report reviews the development of these varieties and documents their yearly spread in statistical terms. Major emphasis is placed on semi-dwarf (1) wheat varieties developed at the International Maize and Wheat Improvement Center (CIMMYT) in Mexico, and (2) rice varieties developed in the Philippines at the International Rice Research Institute (IRRI). Semi-dwarf varieties developed in national breeding programs are also included. Data cover the 10-year period from the 1965/66 crop year, when these varieties first came into wide use, through 1974/75. As of 1974/75, the HYV wheat and rice area in non-Communist nations in Asia and the Near East (including North Africa), totaled about 40.9 million hectares (101 million acres). Of this, about 19.3 million ha. (47.7 million acres) were wheat and 21.6 million ha. (53.3 million acres) were rice. In addition, several million ha. of HYV wheat and about 770,000 ha. (1.9 million acres) of rice were planted in Latin America (excluding Cuba). The HYV area in Africa was relatively minor. Within Asia and the Near East in 1974/75, most of the HYV wheat area and nearly all of the HYV rice area was found in Asia. Over half of the HYV area of both wheat and rice was in India. India was followed by Pakistan in the case of wheat and Indonesia and the Philippines in the case of rice. Altogether, the HYV’s accounted for' about 38.4 percent of the total wheat area and 26.0 percent of the total rice area in Asia and the Near East.