Most exotic maize (Zea mays L.) germplasm is not adapted and, therefore, is not directly usable in U.S. Corn Belt breeding programs. An alternative approach may be to cross unadapted accessions with local testers to explore their potential as donors of favorable alleles. The present study was conducted to determine the effectiveness of the maize race Cateto to improve U.S. Corn Belt hybrids for physical grain quality and other agronomic traits. The Cateto race has been reported to have higher protein, oil, test weight, and hardness than the U.S. Corn Belt Dent race;Inbreds from Uruguay, Argentina, South Africa, and Taiwan representing Cateto, intermediate, and non-Cateto races were crossed to two Corn Belt inbreds, Mo17 and B73, which belong to the Lancaster and Iowa Stiff Stalk heterotic groups, respectively. Eighteen testcrosses (F[subscript]1's), their F[subscript]2 and backcross generations along with four checks were tested at three temperate and two tropical locations in 1989-91. Samples for physical grain quality analysis were only available from the three temperate locations, Ames and Algona (Iowa), and Columbia (Missouri). At these three locations, data were recorded on 1000 kernel weight, test weight, breakage, grain yield, and moisture content;The results showed that the entry crosses that had introgression from inbreds representing the Cateto race contributed favorable alleles for test weight. However, the entry crosses did not show any significant contribution by the Cateto race to improve grain weight, breakage susceptibility, and grain yield;Entry crosses under temperate and tropical environments were evaluated for grain yield, moisture content, days to tassel, days to silk, ear height, stalk lodging, and root lodging. The results showed that Cateto race did not contribute favorable alleles for grain yield, however, the mean grain yield increased considerably by increasing the contribution of adapted dent inbreds to 75%. Days to tassel and silk were less under the tropical environments presumably indicating the effect of cold soils that slows down crop growth rate at early stages in the temperate regions. In spite of the significant entry x location interaction, both temperate and tropical environments ranked the entry crosses similarly.