Endogenous oscillators control the variety of physiological and behavioral circadian rhythms of almost all life forms from bacteria to humans. The suprachiasmatic nucleus (SCN)is the master circadian pacemaker that controls most physical circadian rhythms such as sleep/wake cycles,body temperature, blood pressure, heart rate, hormonal secretion and metabolism, as well as behavior in mammals. Numerous studies at the molecular level have suggested that the circadian oscillator in the SCN is driven by negative feedback loops consisting of the periodic expression of clock genes. Studies of clock genes in mammals have implied that oscillatory mechanisms function in various peripheral tissues such as the heart,lung,liver,kidney,and circulating blood cells, and that they are entrained to the SCN. Although the peripheral oscillators seem to play an important role in regulating various physiological functions, the circadian oscillatory mechanism in peripheral tissues remains vague. We are trying to understand the circadian regulation system in the organism at the molecular levels. 　Recent studies on the clock genes reveal the relationships between the circadian clock and the appearance or symptom of various diseases. Moreover, increases in the sleep disorders, depression, and the neurosis etc. are also thought to be associated with the circadian clock disturb in the 24 hours society. Development of a novel treatment method through a circadian clock regulation seems to become possible, because strong connections exist between the circadian clock disruption and the metabolic disorders under various diseases. We are aiming to pay attention to not only the contribution to the time-dependent medical treatment and the chronopharmacology fields but also the relationships between the lifestyle (especially, feeding habit and mental stress) and circadian clocks at a molecular level, and to contribute from a preventive viewpoint to the public health medical treatment. 　1)Molecular mechanisms of the circadian rhythm generation by the biological clock in culture cells to animals 　2)Search for functional molecules that potentially regulate the circadian clock. 　3)Relationships between the circadian clock and various diseases such as metabolic diseases (diabetes, obesity, and thrombosis), cancer, sleep disorders, depression, and other mental stress.