The anthropogenic radionuclide 137 Cs has been extensively utilized as a tracer of geomorphic processes in the northern hemisphere since its deposition during atmospheric testing of nuclear devices in the 1950s and 1960s. The distribution of bomb-fallout 137 Cs was measured on a sequence of coastal dune sands and soils at Pinery Provincial Park, on the coast of Lake Huron in southern Ontario, Canada. The depth distribution within the stabilized, developed soils inland reflected the relationship between clay content and the adsorption and immobilization of the radionuclide. However, the influence of soil organic matter, silt-sized particles and vegetation cycling on the profile distribution could not be discounted. Within the geomorphically dynamic dune sands near the coast, there was a significant activity of 137 Cs even though the sands were lacking in clay-sized particles. Within a buried soil on the inland side of a large active dune blowout, the distribution of 137 Cs with depth was useful as a stratigraphic marker of the rates of accumulation of sands at that position. Therefore 137 Cs may be a useful alternative to erosion pins, sequential air photos and sediment traps in the monitoring of dune destabilization in coastal environments.