The uses of infrared and ultraviolet spectroscopy in grease analysis are illustrated by showing how mixtures of soaps, different forms of soaps, and additives may be rapidly identified. However, for complete characterization of the soap, particularly when dealing with mixed metal greases, it is necessary to identify the metals present using other means (for example, emission spectroscopy). The identification of greases containing mixed metal soaps, and the occurrence of different forms of soaps are discussed. It is shown how the soap content of a grease may be determined when the base components are known, and a method is given for the estimation of sodium nitrite. It is also shown how aromatic amine type antioxidants may be identified using ultraviolet spectroscopy.