Pentachlorophenol (PCP) is a strong biocide which has been widely used industrially. Releases into the UK environment have resulted in PCP being detectable in most matrices. A budget approach has been adopted to predict the total PCP load of different UK environmental compartments. It is estimated that about 53 tonnes of PCP resides in the UK's non-directly exposed environment, with 94 % being associated with the soil. If contaminated sites are incorporated into the budget, an extra 30 tonnes may be included in which the PCP is also predominantly associated with soil. Releases of PCP to the environment occur mainly as a direct result of industrial activities. However, minor releases of PCP can occur as a result of combustion of waste/fuel or via secondary sources such as the application of sewage sludge to land. It is estimated that of the 300 to 400 tonnes of PCP that has been used annually by UK industry over recent years, over 100 tonnes are released directly via spillages, volatilisation or associated with wastewaters. From the budget and the source inventory it appears that the present UK burden of PCP approximates to about half the yearly PCP flux. By implication there have been substantial losses of PCP introduced to the UK environment, most likely by photolysis and biodegradation.