In order to make optimum use of the Great Lakes, the adverse effects of these wastes must be minimized. To do this, one must be able to quantitatively predict the transport, fate, and effects of contaminants in the Great Lakes. This requires an understanding of how and where are contaminants transported, and what are the biochemical transformations affecting this transport. Since most contaminants are associated with particulates, special attention is given to the transport of particulates although similar arguments apply to dissolved substances. To give some indication of how biological and chemical transformations affect the fate of contaminants, a brief discussion of the effects of these transformations on the transport and fate of several important and representative contaminants is given.