For the decoration of the Studiolo in his palace in Urbino, Duke Federico di Montefeltro called upon an artist who knew how to color with oils . This technique was not yet very diffused in Italy, and it was a Flemish painter, Justus of Gand who was chosen. In this Umbrian city, Justus began to paint the one hundred and eight Portraits of Illustrious Men for Federico. Today, fourteen of these works are in the Louvre, in Paris, and another fourteen have returned to their original site from various places. The article examines the European collaboration between Justus and the Spanish painter who finished the project, Pedro Berruguete. During the restoration of these work at the Louvre, done from 1984 to 1989 by the Service de restauration des musees de France, a careful study of the paintings and scientific analysis permitted the identification of the diverse cultural components that went into their making in this European worksite. The article compares and contrasts these working methods with the norm in central Italy at the time.