The purpose of the present study was to assess the relationship between sediment composition and biological community structure in mixed sands and gravel deposits of the eastern English Channel. Although some species are clearly associated with particular sediment types, the results confirm the lack of correspondence between community composition of the benthos and particle size distribution in unconsolidated sand and gravel deposits. The results also suggest that sample-to-sample variability commonly recorded in the species composition of macrofauna may reflect significant under-sampling by conventional grab sampling techniques. The implications of this for environmental monitoring and impact studies is discussed.