Eight major reviews are cited to indicate a recent knowledge explosion on the use of marine parasites as potential indicators of pollution. A literature update is given for the period 1995–2001. An analysis of the publications cited is used to provide 10 refined criteria for selecting parasites as indicator/monitor species. Previously unpublished data on Diclidophora merlangi and Dictyocotyle coeliaca confirm their value as potential indicators of hydrocarbon pollution in the North Sea. An extensive knowledge of D. merlangi is summarised to emphasize its potential value as an indicator species and also to encourage studies on the health status and immune responses of its host when subjected to pollutant stressors and infection with this monogenean. A discussion focuses on publications which have reported significant recent advances in this area of research and also on accompanying issues, problems and controversies. These selected publications are used to suggest species, stages in the development of species and assemblages of species worthy of further more detailed investigations into their value as indicators/monitors of pollution. It is predicted that further good progress will be made when contaminants can be accurately identified, their precise effects on both host and parasite can be measured by histochemical and biological methods and the roles of contaminants and parasites in causing disease can be assessed separately. About 100 references are cited.