As part of a programme to establish the background levels of PCDD/Fs in milk in the U.K., samples of cows' milk were collected from farms in Derbyshire in 1990 and 1991. The concentrations of PCDD/Fs in the samples from two farms in the Bolsover area of Derbyshire were found to be significantly elevated compared with the normal range for PCDD/Fs in milk in the U.K. Details of the findings and the actions taken as a result are given. The concentrations of PCDD/Fs in milk from those farms previously supplying milk for human consumption are now below the Maximum Tolerable Concentration of 17.5 ng TEQ/kg fat.