Thirteen winter and intermediate type bread wheat cultivars were evaluated under dryland conditions over a four year period from 1991 to 1994 and over 120 environments in the Free State province of South Africa. The Additive Main Effects and Multiplicative Interaction (AMMI) statistical model was used to describe genotype-environment (G × E) interaction of yield performance under dryland conditions. In all three relatively homogeneous production regions, viz. Western, Central and Eastern Free State, the AMMI model identified distinct patterns of adaptation. The hybrids and long growth period pureline cultivars generally had superior adaptation to high yield potential conditions, while the short and medium growth period pureline cultivars were better adapted to lower yield potential conditions. The AMMI model indicates that it can effectively summarise patterns of adaptation of winter wheat genotypes and similarities of Free State environments, as well as offer a valuable prediction assessment.