Recently, measurements by the Superconducting Submillimeter-Wave Limb Emission Sounder (SMILES) satellite instrument have been presented which indicate an increase in mesospheric HO.sub.2 above sprite-producing thunderstorms. The aim of this paper is to compare these observations to model simulations of chemical sprite effects. A plasma chemistry model in combination with a vertical transport module was used to simulate the impact of a streamer discharge in the altitude range 70-80 km, corresponding to one of the observed sprite events. Additionally, a horizontal transport and dispersion model was used to simulate advection and expansion of the sprite air masses. The model simulations predict a production of hydrogen radicals mainly due to reactions of proton hydrates formed after the electrical discharge. The net effect is a conversion of water molecules into H+OH. This leads to increasing HO.sub.2 concentrations a few hours after the electric breakdown. Due to the modelled long-lasting increase in HO.sub.2 after a sprite discharge, an accumulation of HO.sub.2 produced by several sprites appears possible. However, the number of sprites needed to explain the observed HO.sub.2 enhancements is unrealistically large. At least for the lower measurement tangent heights, the production mechanism of HO.sub.2 predicted by the model might contribute to the observed enhancements.