Ever since its establishment in 1919, the Forestry Commission has taken an active interest in the afforestation of heathlands dominated by the common heather, Calluna vulgaris. These heaths hold a large reserve of plantable land, but are difficult areas for the good growth of most timber trees. Much research work has therefore been carried out on their problems, from several angles of approach. This bulletin presents the results of enquiries into those heathland mycorrhizal associations—that is the inter-relationships between trees, plants, and fungi, which appear to be important to the practising Forester. It summarises work done at intervals over the past sixteen years, mainly at Oxford but also at several of the Commission’s heathland forests, notably Allerston in Yorkshire and Wareham in Dorset.