Infrared multiple reflectance spectra were used to record the growth of oxide films on copper and iron mirrors. Cuprous oxide and cupric oxide films were readily distinguished since they exhibit intense single bands at 640 cm−1 and ∼560 cm−1, respectively. Iron oxide films of a single composition also exhibit highly characteristic bands in the 230 to 1100 cm−1 region of the reflectance spectra. Spectra of mixed iron oxide films were composed of many highly overlapping bands making quantitative interpretations difficult. The intensities of the infrared bands from the copper oxide and iron oxide films were directly proportional to the oxide film thicknesses. Using a seven reflection −73° incidence optical accessory, sensitivity to detect oxide films as thin as about 5Aå was achieved.