Information regarding the state-of-the-art of NO(x) (x = 1 to 2) monitoring instrumentation has been assembled and evaluated. The evaluation was based on the present and projected requirements in stationary source emissions monitoring, the operational characteristics and performance capabilities of the instruments, and on the cost/performance criteria. Commercially available and prototype instruments, and laboratory-stage instrumental methods are covered. Instruments based upon wet chemical methods were excluded. The design and operational features of seven instruments which are undergoing laboratory and on-site evaluation at a fossil fuel burning installation are described. Sixteen other NO(x) analysis concepts were also evaluated. Chemiluminescence, correlation spectrometry, mass spectrometry and selective photoionization have been identified as the preferred analysis methods upon which new NO(x) emissions monitoring instruments can be based, using currently available technology, to meet the performance requirements. Novel and potentially useful monitoring techniques, based on the evolving laser technology, were identified.