Unless one is teaching the mechanisms of urinary concentration and dilution to medical students or graduate students, it is best to stay away from countercurrent multiplication mechanisms and concentrate more on the physiological results. When one is teaching medical or graduate students, an overview of the basic countercurrent multiplication and exchange mechanisms is important, because it provides a conceptual foundation for an understanding of water balance. In order not to lose the forest for the trees, teaching aides including demonstrations, relevant clinical examples, contemporary cellular and molecular findings, and a little comparative physiology can be mixed in with traditional educational approaches. In this paper, the teaching of urinary concentration and dilution is first addressed by an educational philosophy synopsis, followed by an outline of the basic mechanisms of urinary concentration and dilution and a presentation of some useful teaching aides. Common student questions are also discussed. This material can be wonderfully fun to teach and is extremely important. The danger is in getting bogged down in explanations involving overly complex mechanisms.