Technical Abstract: New discovery and application of molecular genetics to cattle breeding is occurring rapidly. In this invited paper, we briefly review domestication, migration and classical genetic improvement of beef and dairy cattle. This introduction is followed by a more comprehensive review of genome mapping resources, detection of quantitative trait loci, contemporary use of genotypes in breeding cattle, and future advancements in breeding based on molecular approaches. This review is of value to readers in providing 1) a reflection on the current state of this rapidly changing field and 2) points of access to resources addressing the various topics.