The stability of the luminescence from porous Si has been improved by rapid thermal oxidation. As-prepared and oxidized samples have been compared by cathodoluminescence and photoluminescence. Electron beam excitation resulted in rapid decay of the porous Si emission from as-prepared samples. Photoluminescence measurements from as-prepared samples in oxygen showed a similar degradation. In contrast, the rapid thermal oxidized samples showed a dramatic improvement in stability under either electron beam or photoexcitation.