Adaptability of three-way hybrids of corn and their parental lines to the tropical region of South-Eastern México. During the spring-summer season 1998 and 1999 and fall-winter season of 1997/98 and 1998/99, a research about the adaptability of three-way hybrids of corn and their parents was carried at the Cotaxtla and Isla, Veracruz, Huimanguillo, Tabasco and Apatzingán, Michoacan experimental stations of INIFAP, located in the humid tropic of southeast of México. The objectives of this research were to assess yield, adaptability and agronomic characteristics of the three-way hybrids and their parents. Thus, seven experiments were carried out under an alpha lattice designs with two replications in plots of one 5 m long, 80 cm wide row and 62,500 plants per hectare. The best hybrids were established in validation with farmers during 1999, 2002 and 2003 in Veracruz and Tabasco states. Threeway hybrids were characterized as stable, upper or similar in yield than the control H-513. The best hybrids were: H-513 x CABG3’-10-1-6-1-1-1, which has been suggested for official registration as H-520, (CML247 x CML254) x CABG3’-3-4-2-1-3-1, (LRB14 x D539) x CML254, H-513 x LT157, suggested for official registration as H-518. In validation steps, we found that H-518 and H-520 got similar grain yield to H-513, which participated as female parent in both three-way hybrids. In conclusion, we can say that getting three-way hybrids with good yield and agronomic characteristics represents an alternative to take advantage of heterosis with the additional advantage of seed production.