The technical objective of this SBIR program is to develop and demonstrate metal mesh filters for use in NASA's low noise receivers for terahertz astronomy and atmospheric studies. Metal mesh filters, based on a free-standing sheet of metal with a periodic area of apertures, have been used for many years. However, they have proven to be extremely difficult and costly to fabricate and are not presently available over a large part of the terahertz frequency band (100 GHz through 10 THz). Also, the terahertz filters that are available from commercial suppliers tend to have unacceptable loss in the pass-band (20% or more) and often cost over one thousand dollars per filter. Through this program VDI is developing new fabrication processes and mesh designs that will improve performance and greatly reduce costs. Successful completion of this program will make the filters available for NASA's terahertz missions, facilitate the development of improved terahertz detectors (by facilitating bolometer calibration and testing) and also make the filters commercially available for the greater range of terahertz applications that are now emerging, such as imaging systems and spectrometers.