So intricate, so interconnected are our biological systems that I frequently feel a genuine sense of amazement that the body can work at all, let alone work so well for most people most of the time. However, the sheer number of things that can go physically wrong is also astounding, and it should come as no surprise that disruptions in virtually any body system can result in disturbed sleep. The following pages will offer an overview of some organic conditions that are potential sources of sleeping problems. You may recognize some of the symptoms as your own. But I must caution you about the difficulty of diagnosing your own condition. A symptom—headache, for example—can arise from a spectrum of causes. In any case, I strongly urge you to discuss with a physician any symptoms you experience. Any clues you are able to provide may be just the piece of information needed to understand, and remedy, your situation.