Resonance Raman spectra have been obtained from the MnO4- and CrO4 2- ions in aqueous solutions and as solid. High intensity overtone progressions of the totally symmetric vibration v 1 were observed, allowing estimates of the anharmonicity constants and harmonic frequencies to be made for the v 1 breathing mode. Relative intensities have been measured in the resonance case and correlated with the absorption spectra. Also preresonance intensity data for CrO4 2- have been determined and discussed in terms of an existing theory. The overtone progression of v 1 shows a large increase in half-bandwidth with increasing vibrational quantum number.