Our current knowledge of the Spanish that appears in the corpus of notarial documents from Vizcaya in the fifteenth and sixteenth centuries leads us to raise some problems concerning its place among the dialectal varieties of the central northern regions of the Peninsula. To carry out the present study I have used a corpus of probanza documents [oral testimony] from records of lawsuits, and analysed it from the point of view of its discourse tradition, which only experts in diplomatics (rather than in language) have so far taken into account