A two‐color laser Doppler anemometry technique has been used to measure velocity statistics and Reynolds stress in a turbulent boundary layer over a strongly heated wall (Tw=1100 K) with premixed ethylene–air combustion. Measurements in the isothermal and nonreacting heated wall turbulent boundary layers were also made for comparison. Conditional velocity covariance −∼(uv) are deduced using the quadrant and ‘‘hole’’ analysis methods. The conditional data obtained in the isothermal layer are in exellent agreement with those deduced by others based on hot‐wire data. The results obtained in the heated and reacting layers indicate that the decrease in mean Reynolds stress can be attributed to a reduction in the −∼(uv) contributions associated with a burst of low momentum fluid form the wall. The reduction is much more significant in the reacting layer than in the heated layer. Comparison with previous density shows that the changes in conditional −∼(uv) contributions occur mostly within the constant density sublayer of combustion products adjacent to the wall. In the region where combustion reaction takes place, no significant change in the turbulence intensities or Reynolds stress is found.