A probabilistic method is described for a comparison of nuclear power plant sites in the United Kingdom, which evaluates quantitatively the sites in terms of favourability, by taking into account the real term meteorological conditions, i.e. wind direction, wind speed, and stability distributions, and also the population distribution around the cities. A 'site safety quality factor' is obtained for each site and is used to compare the favourability of each site with respect to releases of radioactivity. The quality factor corresponds to the average number of persons that would be exposed to the specified relative concentration averaged over all weather conditions. The sites compared are Berkeley, Bradwell, Dungeness, Hartlepool, Heysham, Oldbury, Sizewell, and Wylfa.