Measurements have been performed in a 300-MWe, front-wall-red, pulverized-coal utility boiler. New data are reported for local mean gas species concentrations of O-2, CO, CO2, and NOx, gas temperatures, and char burnout measured at several ports in the boiler including those in the burner region. They complement previously obtained data in the same utility boiler before being retrofitted with low-NOx burners and over-fire air ports. During the current experimental work, a considerable effort was made to assure minimum variations on boiler operating conditions and coal chemical and particle size characteristics so that the data presented are especially useful for three-dimensional mathematical model evaluation and development. The main conclusions are as follows: ( 1) As compared with our previous measurements in this boiler, prior to the retrofitting, the results show lower local mean O-2 and higher CO concentrations and temperatures in the boiler as a consequence of the lower stoichiometry in the main combustion zone, after retrofitting. (2) At the lower levels of the boiler the measured NOx concentrations are comparable with those obtained prior to the retrofitting but they are inferior at the upper levels of the boiler, which is consistent with the lower NOx emissions observed at the boiler exit, after retrofitting; specifically, 620 compared with 997 mg/Nm(3) prior to the retrofitting. (3) At the lower levels of the boiler, the high local mean char burnout values measured are due to the combined effects of significant presence of O-2 and relatively large residence times of the particles, while at the upper levels of the boiler the particles residence time is the critical quantity influencing char burnout. (4) Results indicate that carbon is released at about the same rate as total coal mass release while both hydrogen and nitrogen are released more rapidly.