Comprehensive nitrogen species measurements are performed for combustion gases in a premixed, atmospheric pressure, jet-stirred reactor containing 0.1 to 0.6% fuel -nitrogen and 1% fuel -sulfur. Species measured are NO, NH 3 , and HCN by gas sampling, and relative CN and NH and absolute OH by uv absorption spectroscopy. Reactor fuels are C 3 H 8 and H 2 . Nitrogen dopants are NO and CH 3 CN, and the sulfur dopant is SO 2 . Most results are for the conditions: T=1800 K, 1.1≤≤1.7, and 6≤τ≦11 ms. It is confirmed for rich propane flames that sulfur increases NO, NH 3 , and HCN yields, and decreases [OH]. Decreases in CN and NH concentrations are also noted. Kinetic interpretation shows the increase in NO, NH 3 , and HCN yields effected by the depression in [OH] and [H] by sulfur. Less NH and N are formed; therefore, less NO is reduced to N 2 . Also, a shift occurs from CN to HCN, and from NH to NH 3 . The second effect is the weakening of the NO-to-HCN recycle, as sulfur oxides apparently compete for the hydrocarbon fragments required for the recycle. Thus, under some circumstances HCN yields are depressed by sulfur. For NO doped rich H 2 flames, only 15 to 30 percent of the NO is chemically reduced to N 2 . Kinetic interpretation shows that HNO is formed from NO; then small amounts of NH and N form from the HNO. Sulfur weakens the NH and N formation, giving higher NO yield.