(1) Analyses of three heavy metals (lead, zinc and copper) in surface peat layers, dated peat profiles and surface vegetation samples from fifteen British sites are discussed in the context of the movement of heavy metals in the peat system, and the present-day and historical patterns of heavy metal accumulation in humified, slow-growing blanket peat. (2) The concentrations of heavy metals in the surface peat samples provide a basis for the division of the fifteen sites into two groups-'low-background' and 'high-background' sites-reflecting the current urban/industrial status of the sites. Significant regressions were found of the concentrations of lead and copper in the surface peat layers on the loge population of the nearest big town to each site. (3) Dating schemes for five peat profiles were produced by pollen analysis. Generalized linear dating-plots were obtained by correlating individual pollen features with documentary evidence of tree-planting and agrarian or industrial activity. Estimated rates of net peat accumulation varied from 1 cm in 5-5 years to 1 cm in 40 years. (4) Recent rates of heavy metal deposition were calculated for six sites where the rate of peat accumulation had been estimated from pollen analytical/radiocarbon dating. The deposition rates derived from the peat analyses for lead and copper were similar to those obtained by other workers from conventional deposition gauges. The rates for zinc were very much lower than the published figures, suggesting considerable losses by leaching of this metal from the peat surface. (5) Variation in the concentrations of heavy metals was examined in three dated peat profiles. The distribution of lead in a 'low-background' profile apparently reflects national trends in production and utilization of lead during the last seven or eight centuries, while well-marked peaks in the lead profiles at two 'highbackground' sites are shown to correspond well with the documented history of the fortunes of the local lead mines and smelters. The patterns of zinc and copper were less well-defined. (6) In surface samples of present-day blanket bog vegetation consisting of Calluna vulgaris and Eriophorum vaginatum, the concentration of lead was higher in the older, more persistent or decaying plant components, whereas the concentration of zinc was higher in the younger, actively metabolizing organs. In a Sphagnum papillosum sample, the distribution of lead was fairly homogeneous in different age-segments, but the concentration of zinc was higher in the lower, older segments. It is suggested, therefore, that zinc is more mobile within plants and more susceptible to leaching. (7) Two neighbouring peat profiles were analysed for macrofossils. Apparent anomalies in the distribution of zinc were attributed to the differences in the vegetational composition of the profiles. (8) In a laboratory experiment the greater part of the lead and zinc and one-third of the copper in peat blocks was removed by leaching for 24 h with a chelating agent (EDTA). Lead and copper were virtually unaffected by leaching with sulphuric and acetic acids, whereas the zinc was substantially leached by the sulphuric but not by the acetic acid. It is concluded that leaching of lead and copper through peat is unlikely, but that zinc in surface peat is susceptible to leaching, especially in areas