The objective of this study was (a) the development of a measurement technique designed to obtain real-time information on several optical emission characteristics from reactors of entrained-flow gasifiers; and (b) demonstration of the applicability of this technique in the field. The gasifier chosen for field demonstration was the Mountain Fuel Resources, Inc. (MFR) pilot plant located near Salt Lake City, Utah. The MFR plant is an oxygen-blown entrained-flow unit with the capacity of 3000 lb/hr of coal at pressures up to 300 psig. The approach chosen in this study was to make simultaneous measurements of optical emission both from the gas and from coal particles in the interior of the gasifier reactor. These measurements were selected because they provide direct information from the reaction zone, and therefore should provide the most rapid response to changes within the reactor. Characterization of gas emission spectra was made by means of an optical multichannel analyzer (OMA) over the spectral range from about 300 to 850 nm. The intensity of continuum radiation from particles was measured at two wavelengths, and used for time-resolved temperature measurements by two-color pyrometry (TCP). The present study confined itself only to the development of the required diagnostic system and the demonstration of feasibility of such simultaneous (OMA and TCP) measurements in the MFR unit. However, the obvious rationale for the choice of this advanced instrumentation was its usefulness for the future development of reliable on-line monitors for gasifiers.