The commoditization of computer hardware and software has enabled a new computing paradigm whereby computers will sense, calculate, and act on our behalf, either with or without human interaction as best fits the circumstances. Further, this will occur in an everyday environment, not just when a person is working at a desk. This paradigm shift was made possible by the inexorable increase in computing capabilities as we moved from mainframes (one computer, many people) to the personal computer (one computer, one person) to ubiquitous computing (many computers, one person). It is not uncommon to find a single person managing a desktop PC, laptop, cell phone, PDA, and portable media player. Today, these devices are discrete and managed individually. But as ubiquitous computing evolves, the computers will become both more numerous and less visible; they will be integrated into everyday life in a way that does not call attention to their presence. In the context of medicine, ubiquitous computing presents an exciting challenge and a phenomenal opportunity. Proactive computing is a form of ubiquitous computing in which computers anticipate the needs of people around them. Wearable computing results from placing computers and sensors on the body to create a body area network (BAN) that can sense, process, and report on some set of the wearer's attributes. Proactive computing and wearable computing working in tandem let computers fade into the woodwork, enriching quality of life and engendering independence.