Abstract Causa and titulus. Qualifications of possession and a change of terminology in Ulp. D. 5,3,13,1. – In D. 5,3,13,1, Ulpian states that every title to possession (like pro emptore, pro donato etc.) could be accompanied by a general title pro possessore, which becomes decisive if the other title failed. The text is interesting in two aspects: First, it is one of only a handful of classical texts which speak of titulus instead of causa possessionis. Therefore, the text is still today suspected of interpolation. Second, it is heavily disputed which circumstances lead to a possession pro possessore and why this typolology is used at all. This article proposes a solution to both problems. The pro possessore terminology can only be assessed correctly if we focus the procedural position of the possessor, especially in the realm of the hereditatis petitio. The new terminology (titulus) is a mere consequence of the fact, that the burden of prove is assigned according to the ,title‘ of possession indicated by the possessor, not by the real (and possibly unprovable) cause.