Although it is widely recognized that there are significantvariations in the circulation throughout the 24-hour day,these patterns have often been conceived as nuisancevariables rather than functional differences.Responses of the circulation are examined here not as stablephenomena, but as integrated functions highly sensitive toenvironmental conditions, and driven by internal andexternal pacesetters. In this volume, cardiologists with aprimary interest in hypertension or heart disease,chronobiologists, and psychologists join together for thefirst time to give the reader the opportunity to learn theextent and clinical significance of these changes from achronobiological, behavioral and physiological perspective.