The dissociative adsorption of tetraethoxysilane (TEOS) on SiO2 and the subsequent decomposition of the resulting siloxane species has been studied using Fourier transform infrared transmission spectroscopy. The adsorption and decomposition processes have been studied as a function of the initial surface hydroxyl concentration. The results are compared to previous, complementary studies of the surface chemistry of ethanol on SiO2 surfaces and the temperature programmed desorption of TEOS on Si(100).