Ammophila arenaria (L.) Link (marram grass) is the most important sand-fixing plant species along the northwestern European and Mediterranean coast, and it is also planted worldwide for sand dune stabilization. In spite of the intense use of this species in foredune restoration and stabilization programs, little is known about the genetic diversity within and between populations. We analyzed the genetic diversity of seven European populations of A. arenaria using inter-simple sequence repeats (ISSR) markers. The studied populations were selected in Wales, England, Belgium, the Netherlands, Portugal, and France. One half of the populations showed similar values of genetic diversity. The lowest values (Nei's index =0.17) were found in the population from the Netherlands, which had been established after a foredune reinforcement project, and in a declining population in the south of Portugal. Statistical and phylo-genetic analyses revealed genetic differences between populations, and northern and southern clusters that corresponded to the two subspecies of A. arenaria. We propose that plant material for dune vegetation re-establishment programs should be collected locally rather than from remote populations that might be less well adapted to the local conditions of the planting site. However, when using local clonal plant material, care should be taken to collect the plant material from a number of sampling sites in order to ensure the genetic diversity of the new stands.