In this volume of the collection of Medieval documental sources of the Basque Country, devoted to the Municipal archives of Salvatierra-Agurai, a total of sixty two dcuments corresponding to the first half of the 15th century have been transcribed. The documentation transcribed, which belongs to this town in Alava in the proposed chronology, includes various documents of assorted themes. Specially noteworthy among them are those on the lease and collection of the tithes and customs revenue of the bishoprics of Calahorra, Osma and Sigüenza, as well as several confirmations of privileges granted to the town of Salvatierra by the Castilian monarchs Henry III and John II. Also among the transcribed texts there are several concords effected by the council of Salvatierra with other towns, villages and lords of the region, as well as several documents that inform us on the relationships of the town with its Lords: the Lords of Ayala. Finally, the largest texts transcribed correspond to an inventory of the writings and privileges contained in the Archives of the Council of Salvatierra, dated 1429, and on the court case filed by Council of Salvatierra against Fernando Sánchez de Castro by the patrons of the church of Abitona in 1450.