A field survey of the infection of dune plants by vesicular-arbuscular mycorrhiza (VAM) has been made in the coastal sand dunes of the province of North Holland, The Netherlands. Winter annual grasses and herbs are not or nearly not affected, whereas perennial plants, especially the grasses Agrostis stolonifera and Calamgrostis epigeios have a high degree of VAM infection. Seasonal changes of the infection degree generally occur; the highest infection is found in summer. In greenhouse experiments at 20 °C infection could be induced in the dune annual Phleum arenarium by Glomus fasciculatum and G. mosseae. The dune annual Aira praecox, however, could not be infected. This result is discussed in relation to seasonal development and temperature demands of VAM. In greenhouse experiments with Calamagrostis epigeios, infection by Glomus fasciculatum and G. mosseae had no positive effect on growth of, or phosphorus supply to C. epigeios. Both Glomus species cause differential translocation of phosphorus and potassium from roots to shoots of c epigeios. The ecological importance of these results is discussed in relation to the hypothesis of drought protection and nutrient translocation by VAM.