The objective of this study was to assess the representativeness of the test environments used by the maizebreeding program of Embrapa in the first phase of genotype evaluation. Ear weight of 378 hybrids from a diallel of 28 openpollinatedvarieties (OPVs) evaluated in ten environments were used. The following environments were evaluated: twogrowing seasons (1991-92 and 1992-93), at three locations (Sete Lagoas, MG, Londrina, PR, and Goiania-GO); in twogrowing seasons (1991/92 and 1993/94) in Aracaju-SE; and in two growing seasons (1992-93 and 1993-94), in PontaGrossa-PR. The complex part of the interaction accounted for nearly 75% of the genotype by environment interaction (G x E).The environments of Londrina-91/92, Ponta Grossa-93/94 and Aracaju-93/94 differed from the others and also from eachother, as shown by stratification analysis. The phenotypic correlation between genotype means in the pairwise groupedenvironments, interpreted as coefficient of genotypic determination, indicated that non-genetic causes were responsible for64.40% of the mean phenotypic variances. The results confirmed the discrimination of three major environmental groups,representing the Northeast (Aracaju), Central Southeast (Sete Lagoas, Goiania and Londrina) and South (Ponta Grossa)regions