Luoma suggested 25 years ago that tolerant populations could be used to detect adverse ecological effects of pollution. Despite the apparent attractiveness of the idea, there have been few successful examples of its use and a number of failures. Pollution-tolerant populations are limited almost entirely to areas that are grossly contaminated with one or a small number of substances and have flora and fauna that are severely impoverished. Tolerance does provide strong evidence of impact by a particular contaminant but is of limited value as a monitoring tool. Instances of evolved tolerance do, however, have a valuable role to play in environmental risk assessment. They provide model systems for understanding the impact of pollutants on the physiology and performance of individuals and in consequence how they produce effects at the population and community level, in the way that metal tolerance in plants has been used as a model system for the study of evolution. Pollution-induced community tolerance has more promise than population tolerance as a tool for monitoring the effects of pollution, and already has a much longer list of successful applications despite its shorter history.