In the Horizontal Attenuated Total Reflectance (ATR) technique, IR radiation is passed through a crystal at an angle less than the critical angle. This means that the light undergoes total internal reflection. In a sense, the light bounces back and forth through the crystal. At each such reflection, the radiation does penetrate a small distance beyond the crystal surface. If an IR absorber is in physical contact with the crystal, the internally reflected energy is attenuated at those frequencies at which the sample absorbs IR radiation. This technique is useful for films, solids, liquids, powders, etc. It is an easy technique that produces high quality spectra. {insert figure}