The Total Position Spread (TPS) tensor is a key quantity that describes the mobility of the electrons in a molecular system. The computation of the TPS tensor has been implemented for CAS-SCF wavefunctions in the MOLPRO code. This permits the calculation of this quantity for fairly large systems and wavefunctions having a strong multi-reference character. In order to illustrate the possibilities of the method, we applied the formalism to a mixed-valence Spiro-type system. (C) 2013 Elsevier B.V. All rights reserved.