We propose to use the HRPD to establish the sequence of structures, and the nature of the transitions between these, in two complex manganites Sr0.5Pr0.5MnO3 and Sr0.65Pr0.35MnO3. This work will allow us to determine in which structures there is evidence for the JT distortion of the Mn and Pr cations. It is intention to examine the phase transitions via the temperature evolution of both symmetry-adapted spontaneous strains, derived from lattice parameters, and symmetry-adapted (normal mode) coordinates.