A healthy stream is an ecosystem that is sustainable and resilient, maintaining its ecological structure and function over time while continuing to meet societal needs and expectations. The concept described in this paper explicitly incorporates both ecological integrity (maintaining structure and function) and human Values (what society Values in the ecosystem). Stream ecologists who want their research to contribute to improving conditions in flowing waters require concepts Like stream health, which will stimulate research in directions that will be more effective in restoring and preserving the unique organisms and ecosystems they study. Determining what is a healthy stream requires integration of stream ecology with disciplines such as economics and political science, because a concept of stream health must take into account the human attitudes and social institutions that are a part of the stream's societal watershed. New and fruitful directions for stream research lie in developing operational measures of stream health, which include the human dimension and move beyond identifying symptoms of ecological stress, and in elucidating the ecological processes and human actions that maintain stream health.