Concentrations of PCBs and PAHs have been determined from the individual sections of peat cores obtained from an ombrotrophic bog in rural north-west England. Chronological intervals throughout the core were determined from both radiometric (210Pb, 137Cs, 241Am) and independent, non-chemical characteristics (pollen, magnetics) information. Net fluxes of 25 individual PCB congeners and 14 PAH compounds to the bog were then derived. PCB inputs were apparent from the late-1930s/ early-1940s, with maximum sub-surface fluxes ( 1300 pg cm−2 year−1) observed at a depth corresponding to 1964. Loadings decreased by 65% over the following 15 year period before showing a surface enrichment. Initial increases in PAH loadings appear to coincide with the beginning of the Industrial Revolution, with fluxes peaking in the early-1930s (305 ng cm−2 year−1). Introduction of emission controls and the decline of heavy industry has led to an 80 % reduction in the net flux of PAHs to the bog over the last three to four decades. Potential effects of postdepositional diagenesis are considered, with particular reference to alteration of contaminant chronologies.