This contract funded a Satellite Symposium on the Mathematical Modeling of Circadian Systems which was held on June 21, 1981 in conjunction with the Annual Meeting of the Association for the Psychophysiological Study of Sleep (APSS) from June 17-21, 1981, at Dunfey's Hyannis Hotel on Cape Cod, Massachusetts. The Satellite Symposium brought together the leading investigators concerned with modeling the circadian system to ensure that the various proposed models were critically reviewed and their strengths and weaknesses in predicting periodic biological phenomena were fully understood. The papers of each participant and an edited transcription of the discussion were published as a book entitled 'Mathematical Models of the Circadian Sleep-Wake Cycle' by Raven Press in 1984. The published volume serves as an important source of all those who are concerned about the temporal organization of human and animal behavior and physiology. (Author)