We are requesting support for the biomedical part of the program of the Fourth International Conference on Complex Systems being planned for June 9-14, 2002. This event will build on the successes of the three previous conferences: (a) International Conference on Complex Systems (September 26-30, 1997), (b) Second International Conference on Complex Systems (October 25-30, 1998), and (c) Third International Conference on Complex Systems Institute (NECSI), is the main international conference dedicated to the unified study of complex dynamical systems. In the upcoming ICCS, we are planning the topical last day of the conference (consisting of two plenary sessions) to be devoted to evolution, and one of the other plenary sessions to be on the development of complex systems approaches to biological systems. Together these three sessions would be approximately 12 out of a total of 26 plenary talks. Our request is for support of the presenters of the biomedical topics and of students and postdocs. NIH's interest in promoting projects that involve applications of tools from mathematics, physics, computer science and engineering to complex biological systems will be advanced by this conference. The conference will expand the community that can contribute to this objective by providing biomedical students and researchers with background on the concepts and methods in complex systems, and informing other students and researchers about the current research issues in biological systems. Central to the purpose of the conference is building the connection between traditional and modern mathematical modeling and fields that have a new need for such modeling, specifically the biological sciences. NECSI is an educational and research institution with the participation of faculty from major academic institutions from New England, around the United States, and internationally. It is dedicated to interdisciplinary communication and collaboration on the study of complex systems. There is a new and growing effort to understand complex systems and complexity that has attracted wide-ranging interest in the scientific community. Various conferences and workshops have addressed aspects of these growing efforts. However, this is the only major international conference series to bring the wide diversity of researchers together, demonstrating the interdisciplinary but coherent nature of these efforts.