Relatively few statistical sample surveys have been caried out on lakes and streams but these can play an important role in characterizing the biological conditions of lakes and streams. Some of these are described to illustrate how the concepts of sample surveys have been implemented for a variety of purposes and the nature of the conclusions that can be drawn from sample surveys. Specifically, sample surveys can be used to characterize the range of biological conditions found in lakes and streams statewide, or in specific parts of a state, without monitoring each lake or stream. These kinds of surveys can be used as a foundation for establishing numeric biological criteria.