||Through the decade of the 1960s and into the early 1970s, while both area and production of wheat were on an increase in Brazil, the country did not enjoy the benefits of the "miracle seed" of Mexican varieties that were creating a "green revolution" elsewhere in the world. The foremost restriction on the adaptation of the early semidwarf wheats from Mexico to Brazil was their extreme susceptibility to toxic levels of aluminum and manganese and phosphorus deficiency encountered in the acid soils of the region. In spite of heavy applications of industrial lime to neutralize the acidic effects and also help boost the growth of the soybean crop during the summer season, "crestamento" (crop burning) remained a serious problem for Mexican germplasm. By the mid-1970s, it became clear to CIMMYT breeders that Brazil was not an isolated case with acid soil/roblems, in fact many other wheat growing regions in Africa and Asia ha similar problems. The first steps to combine the tolerance of Brazilian wheats to aluminum toxicity with the semidwarf stature, high yield potential, and wide adaptation of the Mexican wheats were taken in the mid-1970s. The informal collaborative shuttle breeding relationship between Brazil and CIMMYT started in 1974 through the efforts of N.E. Borlaug, then director of the CIMMYT Wheat Program and scientists at the National Research Center for Wheat (CNPT) of the Brazilian Agricultural Research Enterprise (EMBRAPA), the Rio Grande do Sul Federation of Wheat Soybean Cooperatives (FECOTRIGO), and the Organization of Parana State Cooperatives (OCEPAR). Later this collaboration was expanded to include the Parana Agronomic Institute Foundation (IAPAR), the Cerrados Agricultural Research Center (CPAC) ofEMBRAPA, and the Campinas Agronomic Institute (IAC). Under this shuttle breeding operation, crosses between the two germplasm pools (Brazilian and Mexican) are made at both ends and subsequent generations are alternated and selected under local soil and disease pressures. To speed this process up, in the late 1970s, CIMMYT's aluminum screening laboratory began operation at El Batan to enable the screening, in Mexico, of segregating and advanced lines for tolerance to aluminum. Sometimes the materials of the same generation are grown simultaneously in Brazil and Mexico. Notes on tolerance to aluminum are telexed to Mexico to permit selection for disease and agronomic characteristics only among the lines already determined to be aluminum tolerant. After 12 years of collaboration, many breeding advances have been made, including the transfer of the aluminum tolerance gene to the semidwarf wheats. This has resulted in new Brazilian varieties that have a yield potential 30% over that of the old varieties under Brazilian conditions while maintaining the aluminum tolerance characteristic. In the early stages of this collaboration, the major benefactors of this work have been the Brazilian institutions. However, in view of the vast areas worldwide with soil acidity, the Brazilian institutions and CIMMYT agree they should share the responsibility for distributing the germplasm resulting from this collaboration to other countries with acid soil problems. Representatives ofEMBRAPA, FECOTRIGO, OCEPAR, IAPAR, IAC, and CIMMYT met August 13-15, 1986, at Foz do Iguacu, Parana, Brazil to evaluate the results of over a decade's collaboration. The second objective of the meeting was to analyze the need to continue with the shuttle breeding efforts to further develop germplasm with a higher degree of aluminum tolerance and to identify additional limiting factors to the development and spread of high yielding wheat varieties in both traditional and newly-opened acid soil regions. The papers in these proceedings report on the breeding progress and plans for the future. Further research to improve the resistance of the new germplasm to climatic factors such as drought, heat, and frost as well as to diseases and insect pests is essential to broaden future adaptation. A new look into the needs of crop management research for the marginal production areas will help develop technologies that will allow the new germplasm to reach its potential. We hope that the deliberations at this meeting will not only increase the collaborative work between the Brazilian institutions and CIMMYT, but also will lead to the participation of many other wheat scientists facing similar problems around the world. Today's shuttle breeding program may be the beginnings of tomorrow's shuttle breeding network.