Within the frame of the 2nd Iberian Congress of Environmental Contamination and Toxicology (University of the Basque Country, Leioa, June 1998) a workshop was held about the use of biomarkers in marine pollution monitoring. Among others, the following biomarkers received special attention: metallothionein induction, acetylcholinesterase inhibition, cytochrome P450 system induction, imposex, lysosomal enlargement and lysosomal membrane destabilisation, and peroxisome proliferation. These biomarkers can be used to evaluate exposure to and effect of different contaminants (metals, organic xenobiotics and organometallic compounds) and they can be measured using different methodological approaches (biochemistry, cytochemistry, immunochemical methods based on the use of biotechnology). Before the application of a set of biomarkers in pollution monitoring programmes, well-defined protocols of Quality Assurance have to be established to allow adequate comparison of results. It is also necessary to include analysis of standard reference materials and to obtain detailed knowledge of basal values and seasonal variations of the biomarkers in various species, as well as to integrate the information obtained with the different biomarkers. Marine bivalve molluscs such as mussels are appropriate sentinel species for most of the biomarkers proposed except for the induction of the cytochrome P450 system, which should be measured in fish, and the degree of imposex, which is a biomarker of exposure to TBT specifically measured in certain gastropod molluscs. As a result of the workshop, a battery of biomarkers of contaminant exposure and effects are proposed that could be incorporated into programmes monitoring the quality of the coastal environment in the Iberian Peninsula. These measures would be undertaken in conjunction with chemical measures of contaminant burdens in selected sentinel species.