This proposal is a request for partial support of the Second Meeting of the Society for Research on Biological Rhythms at Amelia Island Plantation, Florida on May 9-13, 1990. The conference will cover a number of topics in the area of rhythms including neural and cellular oscillators, pulsatile and ultradian rhythms, circadian rhythms and annual cycles. The levels of research interests range from molecular genetics, biochemistry, and cell biology to physiology, neuroscience, and clinical applications. This broad coverage of rhythmic phenomena in living systems is a reflection of the goals of the Society which are to promote the advancement of scientific research in all aspects of biological rhythms, to disseminate research results concerning biological rhythms to the general public, to develop and enhance the education and training of students and researchers in this field, and to foster interdisciplinary communication. The organization of the conference will be similar to the First Meeting of the Society which was held at Wild Dunes, South Carolina on May 11-14, 1988, except that the meeting will be extended to three full days in 1990. The meeting will have symposia, workshops, oral presentations and poster presentations. there will be six major symposia on topics of broad appeal featuring invited speakers with two symposia held each morning for three days. The symposia are scheduled to cover the following topics: 1) Mutations to study molecular mechanisms of rhythms; 2) Shift work; 3) Cellular models of circadian rhythms; 4) Mechanisms of photoperiodism; 5) Interval and developmental timing; and 6) Mammalian pacemakers: is the SCN the only one? Approximately twelve workshops will be held on various specialized topics. Approximately twelve slide presentation sessions will be held from submitted abstracts and poster presentation sessions will be held from submitted abstracts. The first meeting of the Society was a great success with almost 300 participants attending. With the continued growth of the Society with over 300 members from sixteen countries, we expect the second meeting to exceed the attendance of the first meeting.