Natural gas reburning is a mature, commercial NOx control technology involving combustion of a fuel in two stages that has been successfully demonstrated at full scale. In a specific range of process conditions NOx concentrations can typically be reduced by 60%. The Advanced Reburning (AR) process, a combination of basic reburning and Selective Non-Catalytic Reduction (SNCR), can provide up to 85% NO reduction. Recent reburning research has focused on developing improved AR techniques to obtain up to 95% NOx control. Novel AR methods incorporate injection of N-agent promoters (sodium salts), N-agent injection into the reburning zone, and two stages of N-agent injection for deeper NOx control. An important consideration with these innovative reburning technologies is whether they generate toxic byproducts. An experimental program to evaluate byproduct emissions from different reburning technologies was conducted in a 250 kW Boiler Simulator Facility. Species evaluated included CO, CO2, NOx, N2O, SO2, SO3, total hydrocarbons, NH3, HCN, and fly ash. The goal of the program was to compare byproducts emissions From AR methods to those from existing commercial NOx control technologies. Experimental data are presented on byproduct emissions for different innovative AR technologies. The results show that AR technologies can be applied without significant adverse environmental impacts. In most cases, emissions from AR are lower than those from commercial technologies.