417 animals were analysed in all: 147 pottokas, 163 Basque mountain ponies, 62 Jacas Navarras and 45 of the Burguete horse breed. Two of these breeds are heavy or given over to meat production (Jaca Navarra and Burguete); on the other hand, the other two are considered to be lightweight breeds... one can observe a gradient between the autochthonous breeds: the pottoka has had the least external influence and the Burguete breed the most... The results show that the four native breeds are related to each other; above all there are geographical relations: the pottoka with the Basque mountain pony...