Water pollution is perceived by the general public to be of increasing concern as a major problem facing the state. From a survey of a representative sample of adults in Wisconsin, it was shown that the public has rather definite ideas about what constitutes a description of pollution. The respondents mentioned algae and murky, dark water but did not often mention attributes such as chemicals or disease germs that are not detected by the human sensory system. When the respondents were asked to name water in the state that they felt was polluted, they named waters that in fact have the characteristics they described when defining pollution. The most widely used indicators of water pollution seem insufficient in light of the public definition of, and concern about, water pollution.