An overview is given of EPA's research program to develop improved control technologies for emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) from the combustion of fossil fuels. Analysis indicates that low capital cost technology for retrofit to existing boilers would provide flexibility in control strategy even at moderate (e.g., 50%) SO2 removal rates. EPA is evaluating the Limestone Injection Multistage Burner (LIMB), which combines sorbent injection for SO2 control with the use of low-NOx burners. EPA also is evaluating E-SOx and ADVACATE (ADVAnced SiliCATE) technologies. E-SOx combines advanced electrostatic precipitator (ESP) technology and spray dryer technology to remove particulate matter and SO2 in the same physical equipment; the ADVACATE process uses in-duct injection of a highly reactive calcium sorbent for SO2 control. The process may be used alone or in combination with LIMB to enhance performance. EPA's program for research and development, field evaluation, and demonstration of LIMB, E-SOx, and ADVACATE technologies is described.