CaGeO3 perovskite was synthesized from its wollastonite polymorph at P=8 Gap and T=1000¿C in a uniaxial split-sphere apparatus (USSA-2000). For recovered specimens heated to less than 500¿C at 1 bar, the crystallographic distortion of the orthorhombic (Pbnm) CaGeO3 perovskite, that is the tilting of the [GeO6> octahedra, decreases with increasing temperature in the range 25--250¿C. At temperatures near 250¿C, CaGeO3 undergoes a reversible transformation from an orthorhombic to a tetragonal structure, accompanied by an abrupt increase in the mean thermal expansion. Such behavior is typical of other orthorhombic perovskites and may occur for silicate perovskites in the lower mantle. ¿ American Geophysical Union 1988