Biomass burning in the tropics contributes substantially to the emission of organic compounds and nitrogen oxides into the troposphere and has an important impact on the global budget of ozone in the troposphere. Since ozone formation is a nonlinear chemical process the rate of formation is also influenced by atmospheric dilution and transport. This paper addresses the production of ozone in a plume emerging from a biomass burning site. Atmospheric mixing processes downwind the fire are expected to influence the total amount of ozone produced. A sensitivity study to assess the influence of dilution on the maximum ozone mixing ratio and on the amount of ozone formed in the entire plume (excess ozone) reveals that both quantities depend strongly on the time scale and the final value of the dilution. Up to 70% difference of the excess ozone as function of the characteristic time of the dilution was observed. Since many global models do not treat the early development of the plume with sufficient resolution in space and time a substantial uncertainty of model predicted ozone formation from biomass burning plumes is to be expected. ¿ 1998 American Geophysical Union