Recent threats to groundwater quality in the UK (arising from leaking sewers and burial pits used during the recent Foot and Mouth Disease epidemic) have highlighted the need to understand the fate and transport of pathogenic viruses in the subsurface so that a robust assessment of their potential threat to environmental and public health can be made. Non-hazardous microbial tracers (phage) that mimic the movement of pathogenic microorganisms through groundwater systems are being used. Bacteriophage have good potential as surrogates to help us better understand the fate and transport of viral pathogens and are discussed here in the light of their injection as tracers into UK aquifers. Specific bacteriophages (MS2, PRD1 and phi X174) that exhibit good potential as tracers and have properties similar to pathogenic viruses of interest are discussed. (C) 2006 Elsevier B.V. All rights reserved.