Abstract
The statistical methods for the estimation of genotype-environment interactions based on the concept of genetic correlation are reviewed and the implications of genotype-environment interactions in selection and in performance testing of genetic stocks discussed. From comparative testing of commercial poultry stocks there is overwhelming evidence for the occurrence of stock-testing station interactions. However, the relative importance of the effects may vary considerably between performance traits and between testing situations. In general, the consequences of genotype-environment interactions appear to be more serious in egg production stocks than in broiler stocks. For laying rate and viability particularly large effects have to be expected.