Remote sensing methods offer a number of advantages over contact measurement methods in the area of enforcement and surveillance of emissions from stationary sources. Several techniques have been developed that can measure the gas concentration, effluent velocity, and particulate opacity. The velocity measurement is needed so that a mass emission rate may be determined. To evaluate the accuracy, utility, and state of development of some of these techniques, a series of measurements were conducted at coal-burning power plants in which the results of the remote measurements were compared with the results of in-stack measurements made using EPA Reference Methods. The techniques studied and the properties measured were (1) infrared gas-filter correlation radiometry (SO2); (2) Fourier-transform spectroscopy (SO2); (3) ultraviolet matched-filter correlation spectroscopy (SO2); (4) infrared and ultraviolet television (velocity and SO2); (5) infrared laser Doppler velocimetry (velocity); and (6) visible lidar (plume opacity). The techniques used, procedures, the measurement results, and recommendations for evaluating and using remote sensing instruments for measuring emissions from pollutant sources are described.