1 The concentrations of a range of organochlorine pesticide residues have been determined in 168 samples of human milk collected between January 1997 and May 1998 in the UK. 2 Of the 18 residues sought, only p,p′-DTT, p,p′-DDE, dieldrin, HCB, β-HCH and γ-HCH were detected. 3 The continuing trend of a reduction in the concentrations of these pesticide residues in human milk samples and in the percentage of human milk samples containing residues was seen. 4 Correlations between the concentrations of p,p′-DDE, dieldrin, HCB, β-HCH and γ-HCH and age were seen. 5 When compared to studies carried out in Europe over a similar time period, residues in this present study were shown to occur at similar or lower concentrations.