In this article are studied the technical and doctrinal characteristics of the Italian Commentaries on Aristotle's Poetics in the 16 th Century. The habits of the humanistic Commentary and its doctrinal prejudices are systematized. Especially, are contrasted the Commentaries on Aristotle with those on Horace in akin doctrinal points, emphasizing the false attributions and contaminations, being always favourable to the first one, due to the action of the authority prejudice.