The effect of aqueous cationic and anionic surfactant solution son the chemical stability and photoluminescence (PL) of n-and p-type porous Si has been studied. Exposure of either n- or p-type porous Si to aqueous solutions of the surfactants dodecyltrimethyl ammonium bromide (DTAB) or sodium dodecylsulfonate (SDSulfonate) at less than or equal to pH 3.0 results in quenching of the visible PL from this material via two distinct mechanisms. In the case of the cationic surfactant DTAB, irreversible quenching of the PL is accompanied by chemical corrosion of the porous Si sample, as determined by infrared spectroscopy. The enhanced corrosion rate is attributed to an increase in the reactivity of the hydrides present on the Si surface towards water induced by adsorption of the cationic surfactant. Hydrogen evolution in this reaction was confirmed by gas chromatography. In contrast the anionic surfactant SDSulfonate physisorbs to either n- or p-type porous Si samples, and quenches PL without resulting in a significant amount of oxidation. The mechanism of quenching for the anionic surfactant is attributed to local dielectric effects that increase the non-radiative decay rate in porous Si.