Through the support of the US Army Research Office we are developing terahertz sources and detectors suitable for use in the spectroscopy of chemical and biological materials as well as for use in imaging systems to detect concealed weapons. Our technology relies on nonlinear diodes to translate the functionality achieved at microwave frequencies to the terahertz band. Basic building blocks that have been developed for this application include low-noise mixers, frequency multipliers, sideband generators and direct detectors. These components rely on planar Schottky diodes and integrated diode circuits and are therefore easy to assemble and robust. They require no mechanical tuners to achieve high efficiency and broad bandwidth. This paper will review the range of performance that has been achieved with these terahertz components and briefly discuss preliminary results achieved with a spectroscopy system and the development of sources for imaging systems.