Prior to the sequencing of the Drosophila genome, few would have expected a nephrologist to seek insights into human disease from an animal without kidneys. In fact, several human genes involved in renal disease have counterparts in the fly genome. These genes code for proteins that play crucial roles in the transport of fluid and electrolytes across epithelia. Like all living organisms, flies must excrete metabolic byproducts to maintain homeostasis, but they rely on Malpighian tubules rather than kidneys to move ions across membranes. Both flies and human beings use similar molecular machinery to accomplish the same task. [To view this article, please download the PDF.]