Combustion process modificationss to limit NO//x formation are currently a proven means to control NO//x emissions from coal-fired utility boilers. This technology is generally considered to be isolated from other environmental controls and to have no impact on their design or operation. Regulatory trends toward further significant reductions in NO//x emissions would not likely change this situation if advanced combustion controls now under development are deemed adequate for control. An exception is the apparent suppression of fine particulate generation in low-NO//x boilers which may impact the performance and selection of particulate control devices. The resurrection of furnace limestone injection for use in conjunction with advanced combustion systems for simultaneous NO//x and SO//2 control would pose plant process integration requirements. Economic and environmental control integration issues would arise if future NO//x regulation mandates the application of ammonia-based postcombustion NO//x flux gas treatment processes. Potential adverse effects on air heater surface integrity, particulate and SO//2 control performance, solid waste utilization and disposal, and water quality are anticipated as well as possible stack emission of process by-products.