Wheat is one of the most important small cereal crops in Tigray region of northern Ethiopia. Productivity in the region has been unsatisfactory. There are a lot of production constraints attributed for this low productivity. The existence of genotype by environment interaction for instance is one of the serious problems. Therefore, this book tries to determine genotype by environment interaction and adaptability study of bread wheat genotypes. In this book, it is clearly discussed how genotypes had shown differential yield response across the environments. This was due to the specific adaptability of the genotypes. Therefore, rigorous adaptability analysis has to be made before drawing varietal recommendation.