This letter reports efficient treatment of NO emission with a transient, nonequilibrium plasma created by pulsed corona discharge. The transient plasma (≈50 ns) is found to reduce NO emission by 50&percent; in a flow of 2–25 l/s with energy cost ≈10–20 eV/molecule, corresponding to a fraction of source power of ≈5&percent;. The efficiency ofNOxreduction is a complex function of parameters that include pulse width, pulse polarity, current density, repetition rate, and reactor design. It was found that the best efficiencies are correlated with a low current density(0.2 A/cm2)and high repetition rate (1 kHz) under high flow rate. Careful optimization of all these parameters is required to reach cost effectiveNOxreduction. ©1997 American Institute of Physics.