As a basis for printed property charts and tables, empirical multiparameter equa­ tions of state have been the most important source of accurate thermodynamic property data for more than 30 years now. However, due to increasing demands on the accuracy of thermodynamic property data in computerised calculations as well as the availability of appropriate software tools, and the ever increasing computer power, such formulations are nowadays becoming a valuable tool for everyday work. This development has substantially increased the number of scientists, engi­ neers, and students who are working with empirical multiparameter equations of state, and it continues to do so. Nevertheless, common knowledge on this kind of thermodynamic property models and on the ongoing progress in this scientific discipline is still very limited. Multiparameter equations of state do not belong to the topics which are taught intensively in thermodynamic courses in engineering and natural sciences and the books and articles where they are published mainly deal with the thermodynamic properties of certain substances rather than with the theoretical background of the used equations of state. In contrast to this, my concern mainly was to give a survey of the theoretical background of multiparameter equations of state both with regard to their application and their development.