An objective technique for identifying potential indicator species using analyses based on the distribution of individuals among species is presented. Benthic community data from 6 different areas in N. W. Europe are analysed. In each case species indicative of environmental change in the area are identified, even from areas where such changes are small and have resulted only in minor perturbations in the local community structure. It is shown that particular species groups are characteristically indicative of each area, and that ubiquitous indicator species comnlon to many areas do not occur. The method is rapid and involves little computation; it is robust and can be used across a range of sample sizes; it is theoretically sound and allows the objective selection of species useful as indicators of pollutant effects.