Demulsifiers are a class of surfactants used to destabilize emulsions. This destabilization is achieved by reducing the interfacial tension at the emulsion interface, often by neutralizing the effect of other, naturally occurring surfactants which are stabilizing the emulsion. Demulsifier performance is routinely characterized using simple test procedures developed for use in the field. Because of the complexity of factors determining emulsion stability and, therefore, the effectiveness of any given demulsifier chemical, the wide variety of fundamental, mechanistic approaches to demulsifier selection often give way to empirical methods. A discussion of some of the common demulsifier performance characterization techniques is given along with some empirical methods for demulsifier selection.