This volume concerns the papal documents and other contacts of the papacy with the Diocese of Burgos in Spain up to the year 1198. The first volume in the subseries entitled 'Iberia Pontificia' is dedicated to the more than 200 registers of the Diocese of Burgos in Castile whose bishops maintained intenstive contacts with the papacy, being directly subject to the Apostolic See. Particular emphasis is placed on the protracted disputes concerning the Diocese borders and claims of ownership that often ended up before the Roman Pontifex. This alone proves the importance of the role of the papacy in the reorganization of the Iberian church order during the Reconquista.