This survey included 109 plants native to the jarrah forest (a mediterranean eucalypt woodland in south-western Australia dominated by Eucalyptus marginata and E. calophylla). Mycorrhizal formation by seedlings of these plants was examined after inoculation with isolates of vesicular-arbuscular mycorrhizal (VAM) fungi, or after growth in intact cores of natural habitat soil containing VAM and ectomycorrhizal (ECM) fungi. These methods were supplemented by examining roots from mature forest-grown plants, so that different methods and criteria for designating mycorrhizal association types could be considered. Most plants had one of the following types of mycorrhizal association: VAM only (56% of species); both ECM and VAM (16% of species); or non-mycorrhizal roots (25% of species, which also had long root hairs and/or cluster roots). Plants with dual ECM/VAM associations often formed ECM more readily than VAM. With the exception of the large and diverse families, Papilionaceae, Myrtaceae and Anthericaceae, plants within a family had consistent mycorrhizal relations, as did the members of most genera.