In the absence of heterogeneous processes, distributions of NOy, HNO3, Clx and HCl in the polar winter stratosphere should be determined by transport. A model simulating distributions of these species in the arctic for January and February 1989 is developed using observed fields of potential vorticity and potential temperature. Comparison of model results with column measurements from the DC-8 indicates conversion of NOx to HNO3, condensation of HNO3, conversion of HCl to ClNO3, and conversion of HCl plus ClNO3 to an unmeasured species. Heterogeneous processes strongly affect abundances of NOy and Clx species in the winter arctic stratosphere. ¿ American Geophysical Union 1990