XPS (X-ray Photoelectron Spectroscopy) is a powerful method for the quantitative chemical characterization of thin films and solid surfaces. In this paper the XPS process and instrumentation will be described briefly, followed by examples that illustrate the power of the technique in the analysis of coated surfaces. All solid materials interact with their surroundings via their surfaces. It is therefore crucial that the surface properties of any material are suitable for the proposed application. Modern, high-performance materials will only be suitable for their intended purpose if their surface properties are correctly engineered. Surfaces are very important in a wide range of materials. A few examples are: glasses, painted surfaces, metals, polymers, biomaterials and semiconductor devices. The need for the engineering of surface properties gives rise to the requirement for the detailed chemical characterization of the surface. XPS provides a method for quantitative chemical analysis of surfaces and thin films and consequently is a valuable tool for the surface engineer.