We investigate the impact of new laboratory studies of N2O5 hydrolysis in aerosols on global model simulations of tropospheric chemistry. We use data from these new studies to parameterize the reaction probability (γN2O5) in the GEOS-CHEM global model as a function of local aerosol composition, temperature, and relative humidity. We find a much lower global mean γN2O5 (0.02) than commonly assumed in models (0.1). Relative to a model simulation assuming a uniform γN2O5 = 0.1, we find increases in mass-averaged tropospheric NOx, O3, and OH concentrations of 7%, 4%, and 8% respectively. The increases in NOx and O3 concentrations bring the GEOS-CHEM simulation in better agreement with climatological observations.