Photodissociation and collision processes in the atmosphere cause significant diurnal variations of short-lived minor constituents, in particular among the group of catalysts HOx, NOx, and ClOx. Results of diurnal variation experiments within the framework of the Oxford zonally averaged model are presented. With 49 collision reactions and 13 photodissociation reactions, the model incorporates the most important processes known at present. The model extends from pole to pole and from the surface to about 60 km with a resolution of &pgr;/19 in the horizontal (~9.5¿) and half a pressure scale height in the vertical (~3.5 km). The basic time increment for the integration is 5 min. Results are compared with experimental data.