This study offers both experimental and theoretical analyses of the neural control of rhythmic movement. The focus is on the structure of the central pattern generators (CPGs), shown to underlie the regulation of rhythmic movements. Also dealt with are sensory and descending control systems as they have an impact of CPGs. The chapters offer comparisons among vertebrates, vertebrates and invertebrates, and types of rhythmic movements. Evolutionary, neurophysiological, physiological and pharmacological approaches are brought to bear on the subject. The chapters which present theoretical perspectives, mathematical analyses or modelling of central pattern generators to a considerable degree draw upon material presented in experimental chapters. In this way the particular relevance of the ideas is clarified. Every attempt is made to make the discussion easily accessible to the non-mathematical reader.