Biomolecular computing is an interdisciplinary field that draws together molecular biology, DNA nanotechnology, chemistry, physics, computer science and mathematics. The annual international meeting on DNA-based computation has been an exciting forum where scientists of different backgrounds who share a common interest in biomolecular computing can meet and discuss their latest results. The central goal of this conference is to bring together experimentalists and theoreticians whose insights can calibrate each others' approaches. The 9th Annual International Meeting on DNA Based Computers was held during June 1-4, 2003 in the University of Wisconsin, Madison, USA. The meeting had 106 registered participants from 12 countries around the world.