Plants occupy an important position in the ecosystem, being directly in contact with underlying soil, and providing food for animals, including humans, at higher trophic levels. Their use as indicators in studies of both natural and anthropogenically derived contamination is diverse. The visual appearance of plants, in combination with the presence of particular key species or assemblages, may provide clues to the occurrence of contaminants in the underlying strata. Chemical analysis of plant material, either collected from the field or from laboratory-based plant growth trials, can also provide a measure of the environmental mobility of a contaminant. This article discusses the role of plants as bioindicators with reference to examples of preliminary contaminated land assessment; air pollution monitoring, and studies into the environmental significance of contaminants in domestic and codisposed refuse.