Measurements and computations were made for profiles of temperature and of concentrations of fuel, CO 2, CO, and NO in counterflow flames of mixtures of C 2H 2, N 2, and air against a pure air stream. The equivalence ratio in the fuel stream ranged from 1.5 to 2.4, and the molar ratio of added excess N 2 to C 2H 2 was 8, giving measured maximum flame temperatures between 1750 and 1800 K at the air-side strain rate, 90 s −1, of the experiment. Under these experimental conditions, the flames are essentially free of soot formation and experience negligible NO production through the thermal mechanism, so that the NO is indicative of the prompt mechanism and dependent on the fuel chemistry. The objective was to test the ability of newly revised detailed-chemistry rate parameters to predict flame structures under these conditions. The results show excellent agreement between measured profiles and numerical calculations, thereby providing support for the chemical-kinetic scheme.