Molecular approaches to genome analysis in livestock are reviewed by discussing the contribution of molecular genome analysis to the identification of the genetic variation underlying phenotypic variation (structural genome analysis) and to the definition of the trait-associated and environment-affected gene expression (functional genome analysis) as an important prerequisite to understanding the formation of a phenotype. Aspects of using mapped ?quantitative trait loci? (QTL) or gene variants as well as the identified trait-associated and environment-affected gene expression profile in livestock production are expounded.