Stream and river ecology has been an exceptionally vibrant and rapidly evolving science since the first edition of Methods in Stream Ecology was published in 1996. The second and third editions have then grown with the science and have directly influenced and assisted in the development of stream ecology as a major scientific discipline. Each chapter that has carried over into the new edition has been updated significantly according to new knowledge. Methods in Stream Ecology, 4th edition, contains new chapters as novel methods and molecular techniques have developed to expand on new research questions and ideas, while some chapters from the previous editions were eliminated or combined to reflect current trends. This new edition provides updated information on streams and rivers as dynamic features of the landscape and vital to sustaining biodiversity and human well-being. Methods in Stream Ecology, 4th edition, is integral to propelling stream and river ecology forward over the next several decades and continuing to provide essential guidance to students, teachers, and aquatic ecologists by offering state-of-the-art teaching and research resources.