An in situ Raman characterization of alpha-Sb2O4 and Sb2O3 is reported. The aim of the study was to understand the spectroscopic behavior of these oxides in oxidizing and reducing atmospheres. No detectable variations in the Raman spectra of Sb2O4 can be attributed to either the loss of lattice oxygen (under reducing conditions) or an incorporation of O-18 (during reoxidation). All the observed spectral changes must be due to changes of the Raman scattering tenser with temperature, suggesting a higher symmetry at high temperatures. H2O present in the gas phase has no detectable influence on the exchange properties of Sb2O4. Sb2O3 used in this study is a mixture of molecular (alpha-senarmontite) and polymeric (beta-valentinite) polymorphs. Under reducing conditions the suboxide Sb2O3-x seems to be formed, and reoxidation in O-18(2) leads to a spectrum different from those of (Sb2O3)-O-16 and (Sb2O4)-O-16. Reexchange in 16(2)(O) Or H2O-saturated O-16(2) does not alter the Raman spectra. This may be explained by a stable incorporation of O-18 into the lattice, thus rendering the reexchange impossible, and by an incomplete oxidation to Sb2O4-x under the conditions applied.