The paper gives results of an evaluation of a multistage combustion modification design, combining two advanced NOx control technologies, on a pilot-scale (0.9 MW) package boiler simulator for in-furnace NOx control of high nitrogen fuel combustion applications. A low NOx precombustion chamber burner, which has been reduced in size (to provide a 350 msec bulk gas residence time) to improve commercial applicability, is being used with 10-20% natural gas reburning, in which staged fuel and air are introduced at the boiler front face to reduce boiler modification requirements. Parametric test results thus far indicate that NOx emission levels can be maintained at less than 0.2 lb (calculated as NO2) per million Btu, or about 150 ppm (dry, at zero % O2), for primary fuel mixtures with up to 4% fuel nitrogen dopant. Gaseous and liquid fuels, with ammonia and pyridine dopants used to simulate fuel nitrogen, are being tested. The ongoing EPA program to further optimize burner design and operating conditions is discussed.