Multiple scattering significantly affects atmospheric photodissociation rates, particularly at wavelengths greater than 290 nm. Incorporating the effects of multiple scattering into a one-dimensional transport-kinetics model led to dramatic changes in the concentration profiles of many trace species: thus it is important to include multiple scattering when model results are compared with observational data. The effect on model sensitivity of including multiple scattering ranged from no change in ΔO3 compared with the pure absorption calculation to significant increase in ΔO3 depending upon the model chemistry. The change in ΔO3 due to multiple scattering was small in comparison with the change in ΔO3 resulting from the varying chemical reaction rates. Variations in surface albedo had little effect on model sensitivity.