The present article reviews the effects of environmental pollution on ion transport, metabolism and shape of teleost red cells. Catecholamines liberated into the blood stream in acute stresses activate sodium/proton exchange across thc red cell membrane causing red cell swelling. The exchanger is inhibited by alkyltin compounds and by methaemoglobinaemia. Amphiphiles increase the potassium permeability of the red cell membrane. Exposure to lead inhibits and exposure to tetrachloro-1,2-benzoquinone activates red cell delta-aminolevulinic acid dehydratase. Resin acids, cadmium, lead and oxidizing agents such as monochloramine induce the appearance of abnormal cell shapes. In addition, environmental contamination is often accompanied by an increased frequency of micronuclei in the red cells. Specifically, this effect has been observed during exposure to benzo(a)pyrene. These, and other, examples show that many red cell parameters respond to environmental pollution. Thus, determinations of red cell ion concentrations, microscopic examination of red cells and assays of red cell enzyme activities could be a useful addition to conventional pollution monitoring studies.