UC San Diego's Department of Bioengineering has three main areas representing different levels of biological hierarchy, each with a specific focus. In each focus area, a coordinated program has been implemented that combines experimentation and theoretical modeling so that the information generated from experimental investigations can be integrated and synthesized by the application of engineering concepts and techniques. The choice of these areas was based on our existing strengths, the potential for development, and the relevance of the field to important medical problems.