Pedigree information on 233,214 animal from the studbook of the Associação Brasileira dos Criadores do Cavalo Mangalarga Marchador, related to 16 ancestors with, at least, 1% of genetic contribution to the actual population were used to describe the genetic structure of breed population. Principal component analyses were used to classify animals of the same genetic basis and to identify possible subdivision of the breed in families or genetics groups. The average relationship coefficient between each one of the ancestors and the actual breed population vary from 4.7%, for the mare Herdade Alteza, to .7%, for the stallion Tabatinga Fanfarra. The actual breed population can be subdivided into five families, represented, in order of importance, by animals related to the ancestors Herdade Alteza and Seta Caxias, Providência Itu and Tabatinga Predileto, Abaíba Marengo, Tabatinga Cossaco and Agaí Miron.
horse; Mangalarga Marchador; principal components; family; genetic group
