Changes in chemical bonds in porous silicon (PS) during 192 days of aging were studied using transmission Fourier transform infrared spectroscopy in combination with photoluminescence (PL) measurement. PS exhibits PL peaking at about 650nm, but the PL peak position does not change much. PL intensity increases with aging time, and the intensity of infrared absorption bands other than CHx(x=1-3) changes. Si-H and SiH2 bands decrease in intensity with aging time. The O3Si-H band intensity increases, then levels off. C=O and O-H bands increase in intensity with aging time, but not in correlation with PL intensity. The Si-O band increases with aging time and is closely correlated with PL intensity. These results suggest that some oxygenrelated effect participates in PS luminescence.