The vertical distribution of PCBs was measured in a dated core from the profundal sediments of Esthwaite Water, U.K. The resulting historical record of ∑PCB deposition agreed well with published U.K. production data. Ratios between the various PCB homolog groups revealed significant compositional variations with depth. Sediments deposited in the last ∼10 years and sediments deposited before PCB production began are both relatively enriched in the less chlorinated homolog groups. When considered with other available data, these enrichments provide evidence for post-depositional mobility of PCBs favoring the more aqueous soluble and volatile compounds. The results lend further support to a growing body of evidence that recyling of PCBs is occurring between the sediments and overlying waters, associated with solubilization and diffusive transport.