Environmental protection policy strives to maintain an environment favourable to human health, agriculture, and the preservation of natural heritage. Infringements upon the environment have been either by sudden deliberate action of man (construction, land reclamation, dams, etc.) or by gradual, insipid stress of chemical and physical agents (chemical substances, heat, noise, radiation, etc.). Indeliberate unwanted stress upon the environment may be measured either by observing biological effects on indicator organisms or by chemically analyzing contaminants in these organisms. In this respect the author pleads for modest, cost-efficient monitoring programmes of limited duration and providing policy related information in a direct way. Biological effect monitoring programmes show limited prospects at this moment.