The neutral chemistry initiated in the upper stratosphere and mesosphere by solar proton bombardment can significantly alter the concentrations of several minor constituents at high latitudes. Production rates of ions and neutral species due to two large proton events are computed, and their effect on the chemistry of the middle atmosphere is investigated with a time dependent numerical mode. The production of odd hydrogen in the mesosphere which results from ion chemistry can reduce the daytime ozone concentration to 75% of its normal value over a limited range of altitude. The diurnal variation of O3 is greatly altered during the particle precipitation. Proton events which cause large ionization and dissociation rates in the upper stratosphere create large amounts of nitric oxide which have a long lifetime before conversion to N2 at these levels. Horizontal transport of this NO to middle latitudes may influence upper stratospheric ozone concentrations on a global scale.