Arbuscular mycorrhizal (AM) associations with higher plants are common in many ecosystems but some plant species are consistently never or rarely infected. These species may differ morphologically or occur in different habitats from species which are usually mycorrhizal. A large data-set on the ecology of British angiasperms was used to test for relationships between the mycorrhizal status of British angiosperms and several morphological and environmental variables (life form, root diameter, seed weight, soil fertility, soil water availability, soil pH and habitat type). No relationship was found between soil fertility or soil water availability and frequency of infection with AM fungi. AM species, however, can grow in habitats with a higher pH than non-mycorrhizal species and perennial AM species occur in a significantly greater number of habitat types than perennial species which are never, or rarely, arbuscular mycorrhizal. Non-mycorrhizal species tend to have thinner roots, smaller seeds and occur mainly in aquatic, wetland and saline habitats.