This book is particularly interesting for both horse breeders and molecular geneticists. Equids (horses and asses) have a particular place in the human culture and history. There are strong arguments for conservation of rare, endangered horse breeds and populations, however the maintenance of native breeds does not result in profitable business.Some populations and namely rare horse breeds need to be re-evaluated yet, others need to be saved from extinction very urgently. Enlisting the aid of modern science gives us many tools for reaching decisions to realize the preservation of different rare populations and not to use solely pedigrees, conformation and historical data. The molecular genetic approach and the phenotypic estimation of the values of different breeds is more and more useful. Hence, it was the right time for Horse Commission of EAAP together with Rare Breeds International (RBI) to perform a session devoted to the topic of progress in molecular genetics of horses. This book summarizes the papers on molecular genetic description of horse breeds and some aspects of evolution of horse species.