Marker-assisted selection (MAS) is a form of indirect selection that depends on the accuracy of measuring the marker and the genetic correlation between them. This chapter describes the development of large numbers of single nucleotide polymorphism (SNP) markers associated with high-throughput automated technology, which has made MAS applicable to whole-genome prediction of breeding values. The chapter explores how these techniques have been successfully trialled in commercial poultry breeding programmes, as well as suggesting how future technological developments may permit the use of whole-genome sequencing rather than high-density SNP chips for prediction of breeding values of selection candidates.