||The publication of this document commemorates CIMMYT's twenty years of service to Third World agriculture. Much has changed during the past two decades: scientific advances have opened up new horizons for research; the needs of the Center's clients (national crop improvement programs) have evolved as they have accumulated experience and expertise; and CIMMYT itself has changed in response to changing circumstances. Yet through it all, the Center has, at its core, remained essentially the same vital, dynamic institute that it was at its inception. CIMMYT's maturity as an institution and its global impact belie its official age of 20 years. In a very real sense, the Center is much older. CIMMYT's origins can be traced back to 1943 and the Mexican Ministry of Agriculture Cooperative Agricultural Program/Rockefeller Foundation, which was initiated to improve Mexican agriculture . The Office of Special Studies (as the program was called within the Ministry) employed at its peak 21 non-Mexican agriculturalists and over 100 Mexican colleagues. This cooperative effort was very effective in helping to improve the country's agricultural sector and, by the mid-1950s, Mexico was approaching self-sufficiency in maize and wheat production. The Mexico/Rockefeller joint venture gave credence to the idea that a small , dedicated group of researchers could influence the course of agricultural development. CIMMYT was itself a result of this collaborative effort, and the success of those earlier days enabled the newly formed Center to respond rapidly and effectively to the spectre of mass starvation in the Indian subcontinent during the late 1960s. Those crisis years gave rise to a sense of urgency among CIMMYT staff, reinforcing their commitment to the Center's mission and modus operandi. Many accounts of those early days have been written . We asked ourselves, "Of what value would yet another account be, and really, what should one say in observing the twentieth anniversary of an institution as dynamic, yet as stable, as CIMMYT?" A consensus emerged that a conventional history was not needed; rather, a description of the "mainstreams of CIMMYT research" and the courses they followed over the past 20 years was deemed appropriate . It was with great confidence that Steve Breth was asked to undertake this task. In Steve we found an individual who is arguably one of the most knowledgeable writers focusing on international agricultural research today. Steve has been associated with agricultural research since 1963, when he joined the USDA as an economist working on a study of agricultural development in West Africa. From 1965 to 1969 he served as an editor for the American Society of Agronomy, and from there moved to IRRI for a five-year stint as a writer/editor. In 1974 Steve joined CIMMYT in a similar capacity, leaving in 1977 to join the IADS communications group. He is now with the newly formed Winrock International Institute for Agricultural Development, and special thanks are due to Robert Havener, President of Winrock International, for giving Steve the time needed to write this publication. With his unique background in mind, CIMMYT asked Steve to view the Center's development in light of the forces that shaped the direction of international agricultural research . In so doing, he provides a better understanding of the Center's character and its evolving role in the agricultural research community. This then was Steve's mandate and is the objective of this publication: to give the reader a sense of the Center, its evolving research agenda and priorities, and to place those distinguishing characteristics in a retrospective context.