Profound progress has been made in the fields of chronobiology and psychobiology within the past decade, in theory, experiment and clinical application. This volume integrates these new developments on all levels from the molecular, genetic and cellular to the psycho social processes of everyday life. We present a balanced variety of research from workers around the globe, who discuss the funda mental significance of their approach for a new understanding of the central role of ultradian rhythms in the self-organizing and adaptive dynamics of all life processes. The years since the publication of Ultra dian rhythms in physiology and behavior by Schultz and Lavie in 1985 have seen a burgeoning realization of the ubiquity and importance of ultradian rhythms within and between every level of the psychobiological hierarchy. The experimental evidence lies scattered through a disparate litera ture, and this volume attempts, albeit in a highly selective manner, to bring together some of the different strands. The editors are very conscious of the omission of many important current aspects; e.g. we have not included any of the fascinating and indeed long and well-established experiments with plants (Bunning 1971, 1977; Guillaume and Koukkari 1987; Millet et al. 1988; 10hnsson et al. 1990) that are widely regarded as having initiated the whole field of chronobiology (De Mairan 1729). Neither have we reviewed recent developments on glycolytic oscillations, since a great deal of the seminal work was already completed by 1973 (Chance et al. 1973).