There has been some confusion in the past as to the original support and format of Raphael's portrait of <i>Baldassare Costiglione. The support of the painting and its measurements have been variously described since the 17th century. This has led art historians to speculate that the painting may have been transferred and had been reduced in size. The differing historical descriptions of the painting may be explained because the painting, painted on linen, had originally been glued to or stretched over a wood panel. Evidence is espoused that Italian Renaissance paintings were frequently mounted in this way. The cusping found along the edges of the painting and the composition of other portraits by Raphael indicate that the painting's present format is that intended by the artist. Copies of the painting by Rembrandt and Rubens are also discussed. -- AATA