||The best-performing maize hybrid sent to Latin America in 1994 as part of the first CIMMYT international hybrid trials, and later used as a regular check in trials, was CML247 x CML254, a cross between two excellent CIMMYT maize lines (CMLs). Since then, many new lowland tropical maize hybrids have been developed. Additional comparisons between newly-developed CIMMYT hybrids and CML247 x CML254 could benefit national programs, seed companies, and CIMMYT work in Latin America. This study sought to identify the best new lowland tropical maize hybrids for Latin America by using head-tohead analysis and estimating their reliability, to replace CML247 x CML254 as a check in CIMMYT hybrid trials. In head-to-head comparisons, nine new hybrids showed significant yield gains over CML247 x CML254. Hybrids CL- 04368 x CL-SPLW04 and CL-02181 x CML269 had the highest yields and showed a reliability of over 0.9, suggesting that both will yield more than the old check in 9 out of 10 cases. Based on yield differences between the best new hybrid and the old check, the estimated genetic gain achieved by CIMMYT’s breeding efforts in lowland tropical maize was 279 kg ha-1 year-1 during 1994-2002. Only two of the hybrids studied showed significant regression slopes with respect to the check hybrid, and their advantages over the check could be due mainly to genotype x environment interaction (G x E). Hybrids CL-04368 x CLSPLW04 and CL-02181 x CML269 will be the new checks in CIMMYT field evaluations in Latin America and could be used by seed companies and public institutions in the region per se or as sources of favorable alleles.