Polycrystalline silicon-germanium alloys with compositions between 5 and 30% Ge were wet oxidized in pyrogenic steam with TCA at 700°C. TEM showed that the columnar structure and grain size, ∼500Å, were independent of composition and did not change during oxidation. Both energy dispersive x-ray spectroscopy (EDS) in a UHV STEM and RBS indicate that for low Ge containing films (≤20% Ge), Ge is rejected from the growing oxide, whereas for films with a greater Ge concentration, some Ge is incorporated in the oxide. In low Ge containing alloys, the average Ge profile was determined by RBS and the local Ge distribution was determined by EDS from the oxide interface to about 500Å deep into the alloy. A Ge rich layer was observed at the oxide/poly-SiGe interface. The Ge concentration at the grain boundaries was found to be at least three times higher than that in the grains. The mean diffusion length of Ge along the grain boundaries, measured in cross-section by EDS, was about 300Å, corresponding to an effective diffusivity of about 6×10−16 cm2/s. Analysis of RBS profiles yielded an average effective diffusivity of ∼1.3×10−14 cm2/s. Both diffusivity values suggest that Ge rejected from the oxide growth front diffuses along grain boundaries since the bulk diffusivity of Ge in Si at 700°C is on the order of 10−22 cm2s/s.