Since 11 September 2001 there has been heightened interest and new urgency in devising sensor systems for the detection of chemical and biological agents. The U.S. Defense Advanced Research Projects Agency (DARPA) soon will begin a major R&D program — called "MoleSensing" — to develop systems of nanometer-scale sensors. The goal is to incorporate sensing elements at densities of 1011 per square centimeter, and to integrate them with electronic nanocomputers also being developed by DARPA. In looking for an operational model for such ultra-dense systems of nanosensors, one need look no further than one's nose and the sense of smell, also known as "olfaction." In olfaction, nature provides us with a molecular-scale sensory system that is without parallel in its sensitivity and broadband effectiveness, as well as in its density. The speakers will present an overview of the lessons that natural olfactory systems offer for efforts to develop artificial nanosensor systems. A review also will be presented of recent advances in nanotechnology for broadband chem/bio sensor arrays, or "electronic noses." This presentation will summarize exciting developments in DARPA's new MoleSensing Program, as well as in ongoing research toward a comprehensive MITRE report on "nose-like" nanosensor systems.