Uhlmann A. Density Operators as an Area for Differential Geometry (30K, LaTeX) ABSTRACT. It is shown how to extend the Geometry of the projective space of pure states, equipped with the Fubini Study metric, to the space of density operators. This results in a variant of the metric of Bures which reflects the maximally possible transition probabilities in the vector rpresentations of general (mixed) states. In particular the geodesics are considered, and it is suggested, that with this metric the set of all density operators becomes a cell of a manifold all geodesics of which closes with length $\pi$. Written version of a talk at the Symposium on Mathematical Physics, Nicolous Copernicus University, Torun 1992.