Aircraft measurements of the Kuwait oil fire smoke plumes during August 1991 examined to estimate the conversion rates of SO2 and NOx (NO+NO2) to sulfate and nitrate, respectively. A method based on evaluating a Lagrangian mass conservation equation for the ratios of SO2 and NOx to CO2 is used to estimate plume dilution and conversion rates. The loss process is expressed as first and second order, and NOx concerntration serves as a surrogate for the oxidizing species in the second-order reaction. Continuous measurements of SO2 and NOx within the smoke plume indicate that SO2 and NOx conversion rates were approximately 1% h-1 and 2% h-1, respectively, 100 km from the sources; further downwind, both conversion rates decreased. A box model is used to simulate the chemistry in the plume; SO2 and NOx conversion rates predicted by the box model were ≥1% h-1 and 2% to 30% h-1, respectively, depending on time of day and distance from the source. The dependence of the modeled conversion rate on the time of day suggests that the conversion of SO2 and NOx calculated from the field data may be the average conversion rate assoicated with nighttime and early-morning chemistry. ¿American Geophysical Union 1994