High-intensity photoluminescenee (PL) was obtained for as-prepared porous Si, which was produced by anodization at high concentrations of ethanol. When the porous Si was exposed to ambient air, oxygen rapidly oxidized the surface of the porous Si, and the PL showed a blue shift in wavelength with a slight decrease in intensity within a short time. In the meantime, oxidation with H2O extended deep into the porous Si layer through rupturing Si-Si, and the PL showed a gradual increase in intensity with almost no change in the spectra.