Electron-emissive materials are poised to improve device performance when physical size, weight, power consumption, beam current, and/or high pulse repetition frequencies are an important issue for competitive performance. Cold cathodes offer potential property improvements over conventional thermionic sources - instant on/off performance, high brightness, high-current density, large transconductance-to-capacitance ratio, or low-voltage operation characteristics. Many extraordinary technologies are developing, some well known, and some new to the electron sources scene. Flat-panel displays are undoubtedly the largest commercial endeavor to which cold cathode source technology is being directed. Advanced microwave power tubes are one of the most technically challenging applications pursued. Other important applications with considerable impact include electron sources for micropropulsion systems and tethers for satellites. Small and stable sources are needed for multibeam lithography, electron microscopes, and other high-tech tools and applications. This book contains papers from two symposia held during the 2000 MRS Spring Meeting in San Francisco, all brought together to provide a single comprehensive profile of this dynamic and still advancing field.