X-ray emission spectroscopy applied to surface adsorbates is an experimental technique that provides an atom-specific projection of the electronic structure. In combination with theoretical density functional spectrum simulations, it becomes an extremely powerful tool to analyze in detail the surface chemical bond. The present review discusses both the experimental and computational techniques related to the spectroscopy and summarizes all applications to surface adsorbates published up to May 2004. The surface chemical bond is discussed in depth for a number of example systems taken from the five categories of bonding types: (i) atomic radical, (ii) diatomics with unsaturated π systems (Blyholder model), (iii) unsaturated hydrocarbons (Dewar–Chatt–Duncanson model), (iv) lone pair interactions, and (v) saturated hydrocarbons (physisorption).