An experiment was conducted to evaluate the effect of introgressing seven different exotic germplasms (Cateto, Caribbean Flint, Mexican Dent, Antigua, BS16, Suwan 1, and Tuxpeno) into two widely used Corn Belt germplasms (BS13(S)C4 and BS26). A 13 x 13 simple lattice design was used and the study was conducted at seven Iowa environments. The treatments included the adapted and exotic germplasm, the crosses and backcrosses between them, and check varieties. The crosses and backcrosses were made by using the parents in all possible combinations to obtain treatments with 100%, 75%, 50%, 25%, and 0% exotic germplasm;Treatments and treatment by environment interactions were observed to be highly significantly different (P ≤ 0.01) for grain yield, grain moisture, root and stalk lodging, and days-to-anthesis. Dropped ears and ear height were highly significant only for treatments. The results for grain yield (q/ha) suggest that the best percentage of exotic germplasm used was 50% (the F[subscript]1 hybrids of crosses between exotic by adapted germplasm). Exceptions were observed for Cateto, Caribbean Flint, and Tuxpeno crossed to BS26. Among the exotic germplasm used, Suwan 1 and Tuxpeno exhibited greater potential for continuing development. Both the Suwan 1 and Tuxpeno used in this study had only two years of selection for adaptation in the U.S. Corn Belt compared with the other exotic germplasms. Without considering the reciprocal crosses, the crosses Tuxpeno by BS13 (72.0 q/ha) and BS13 by Suwan 1 (69.1 q/ha) ranked fourth and fifth in the treatments per se, where the top ranked treatment was the cross of BSSS(R)C11 by BSCB1(R)C11, which yielded 79.4 q/ha. Higher values for midparent heterosis and coefficient of determination were also observed when either Tuxpeno or Suwan 1 were crossed with either BS13 or BS26. The higher values for midparent heterosis suggest that the allele frequencies were complementary in the F[subscript]1 hybrids in comparison with the parents. Overall, BS13(S)C4 combined better with the exotic germplasms than did BS26. With the results observed, the heterotic pattern Suwan 1 by Tuxpeno is suggested for exotic germplasm sources or Suwan 1 by BS26 and BS13 by Tuxpeno if exotic by adapted sources are used.