A qualitative benthos study was undertaken in the Western Baltic in order to find trends in the distribution patterns of the most common spp and taxonomic groups. The characteristics suiting spp and communities for use as indicators are discussed. The main environmental factors considered were the degree of sewage pollution, and the type of substrate. 3 ecological groups of organisms can be distinguished on the basis of their reactions to pollution. Sensitive spp should be investigated most closely in their preferred substrates, those favoured by pollution in the types of substrates in which they normally do not occur in great numbers. Sand bottom and, to a lesser degree, eelgrass assemblages are the best indicator communities.