We report polarized Raman measurements on small single crystals embedded in Y1-xPrxBa2Cu3O7 polycrystalline pellets. The measurements show two-mode behavior in the Cu-O bending mode of the CuO2 planes (B1g mode). The increase in frequency with x of the Ba-Ba stretching mode and the chain copper apical oxygen Cu(1)-O(4) stretching mode is consistent with hole localization on Ba sites due to Ba 5dO 2p covalency. This localization may be related to the suppression of superconductivity in this compound, which increases with increasing x. © 1990 The American Physical Society.