All aspects of the marine chemistry, geochemistry, cycling, fluxes and biochemistry of cadmium are reviewed and discussed. The main sections include: 1. A review summary. 2. The aquatic chemistry of cadmium in terms of inorganic and organic speciation, adsorption on to minerals and particulate matter and desorption remobilization from sediments. 3. The distribution of cadmium in the world's estuaries, seas and oceans and the marine disposal of cadmium-containing wastes. 4. The estimation of the global fluvial and aeolian input of cadmium to the oceans, the input of cadmium to sediments various particulate phases, the anthropogenic influence on cadmium fluxes for this century and the calculation of oceanic residence times based on the data. 5. Some physiological and biochemical effects of cadmium on bacteria, phytoplankton species and marine animals. 6. A brief outline of research needs and analytical methods.