Part I of a two part article on the effect upon dreaming on physical illness briefly explores the historical medico-philosophical antecedents of the notion that dreams can be diagnostic of bodily disease. Modern sleep research findings relating REM sleep to physiologic changes are also explored. The controversy of whether dreams are merely the consequence of random brain activity or whether they are a valid psychological phenomenon is discussed. Six contemporary views of the function of REM sleep are outlined. A seventh (...) view of dreaming, that of a “cognitive monitoring system” is suggested. Like earlier historical notions, it is suggested that dreaming is a cognitive activity that processes bodily cues indicating illness or disease. Part II. presents a clinical compendium of dreams relating to Part I. (shrink)