This general review attempts to pull together information on the principal categories of functional properties of proteins and outline the various factors affecting them from the point of view of the food chemist and technologist. It does not purport to be an in-depth or critical examination, but rather an initial, descriptive effort to provide tentative guidelines and ideas to workers in this field, in order to establish some standard systematic methods and terminology for determining and reporting data on functional properties of proteins for food systems. Furthermore, it is hoped to encourage a more quantative approach to the study of protein functionality, and stimulate research to explain the physiochemical mechanisms responsible for specific functional properties.