Manganese oxides of the general formula A(1-x)B(x)MnO(3) (where A and B are trivalent and divalent cations, respectively) have recently attracted considerable attention by virtue of their unusual magnetic and electronic properties(1-9). For example, in some of these materials magnetic fields can drive insulator-to-metal transitions where both the conductivity and magnetization change dramatically-an effect termed ’colossal magneto-resistance’(1-3)-raising hopes for application of these materials in the magnetic recording industry(1-9). Here we show that in one such compound, Pr(0.7)Ca(0.3)Mn0(3), a transition from the insulating antiferromagnetic state to the metallic ferromagnetic state can be driven by illumination with X-rays at low temperatures (<40 K), This transition is accompanied by significant changes in the lattice structure, and can be reversed by thermal cycling, This effect, undoubtedly a manifestation of the strong electron-lattice interactions believed to be responsible for the magnetoresistive properties of these materials(6-9), provides insights into the physical mechanisms of persistent photoconductivity, and may also find applications in X-ray detection and X-ray lithographic patterning of ferromagnetic nanostructures.