Pollution of groundwater by petroleum products is widespread in the industrialized nations. Such pollution is likely to be found wherever petroleum products have been stored, used or refined. The scale of a pollution incident can, therefore, range from relatively minor beneath an oil storage tank to major beneath a refinery. The remediation of oil pollution is a large industry actively pursued by environmental agencies, oil users and the oil industry itself. There is a voluminous literature concerning such remediation, including manuals of remediation practice and environmental consultants' brochures. Unfortunately there is a paucity of published case histories of remediation programmes to show the effectiveness of various remediation practices. The remediation of pollution from a fuel spill at Heathrow is discussed and this, together with experience from other sites, is used to examine the cause and effect of such pollution incidents. The effect of the oil pollution, and the difficulty of remediation, vary with the location of the incident and the hydrogeological situation. The difficulty of remediation, for example, will increase with depth of the water table and with the proximity of urban areas. The possible strategies of remediation under various scenarios are discussed on the basis of experience in the investigation and remediation of oil pollution.