Many marine and freshwater pollution indices are available for all levels of the system, but all have their problems when used in estuaries. These difficulties are compounded at system level, especially where the goal is the creation of an easily communicated management tool, generally in the form of a simple index that integrates the pollution status over the whole of the estuary. The Biological Quality Index and Pollution Load Index have been suggested as simple and robust tools. They have been used in a variety of estuaries in Europe and the US, yielding values over the full scale from near 0 to a maximum of 10.0. The Biological Quality Index and Pollution Load Index results compare well with other indices currently in use, and the data on which the indices are based also provide diagnostic information that can be used to probe spatial, temporal or contarninant patterns in the system further.