The first edition of this handbook appeared exactly twenty-five years ago. Due to enormous changes in the area of diuretics, the second edition has had to be completely revised. Substantial progress has been made in the functional anatomy of the kidney and in the concepts of how substances and ions are specifically transported across the various nephron segments. No one could have foreseen twenty-five years ago that the late 1980s and the early 1990s have provided us with methodologies to study transport events not only at the single cell level, but even at the level of the single transporter...