Atmospheric pollution over cities accumulates under light wind or stagnation conditions and, on occasion, may be supplemented by transport from distant sources. These conditions cannot easily be predicted by use of the average weather elements. However, material which is useful to decision-makers who are concerned with air pollution problems can be obtained by presenting the data, as in the case of Durban, South Africa, first in terms of the nature and characteristics of vertical mixing in the lower atmosphere, and secondly in terms of the horizontal transport of air. In this way the nature and characteristics of surface and non-surface inversions and mixingdepths, as well as of macro- and meso-scale atmospheric circulations, can more easily be appreciated. In addition, a measure of the air pollution potential can be obtained from daily maximum mixing-depth and win-speed values.