Most of the papers included here were part of the Plenary Sym- posium on The Testing of General Ecological Theory in Lotic Ecosys- tems held in conjunction with the 29th Annual Meeting of the North American Benthological Society in Provo, Utah, April 28, 1981. Sev- eral additional papers were solicited, from recognized leaders in certain areas of specialization, in order to round out the coverage. All of the articles have been critiqued by at least two or three re- viewers and an effort was made to rely on authorities in stream and theoretical ecology. In all cases this has helped to insure accur- acyand to improve the overall quality of the papers. However, as one of our purposes has been to encourage thought-provoking and even controversial coverage of the topics, material has been retained even though it may upset certain critical readers. It is our hope that these presentations will stimulate further research, encourage the fuller development of a theoretical perspective among lotic ecologists, and lead to the testing of general ecological theories in the stream environment.