An experimental program was conducted to evaluate low-NOx combustor concepts applicable to natural-gas-burning aeroderivative gas turbine engines operating at a nominal pressure ratio of 20:1. Gas sampling measurements at the exit of the primary zone of high-shear and lean premixed burners were acquired under elevated entrance pressure and temperature conditions over a range of primary zone equivalence ratios. Piloting systems were incorporated in most of the burner designs to achieve satisfactory burner operability. Both swirl stabilized and perforated-plate (grid) stabilized burners were found to produce NOx levels lower than the current engine goal of 25 ppm (15 percent O2 ).