The investigation was initiated by the Forestry Commission as part of the programme of research into the afforestation of heathlands. The object of the investigation was to study the root development of coniferous forest crops on upland heaths to determine: (i) The relationships existing between the development of the root systems, the soils, and the types and intensities of cultivation prior to planting. (ii) The effects of the application of fertilisers on the vigour of the root systems. (iii) Differences occurring in the root systems of the species studied. (iv) The comparative ability of the root systems of these species to exploit the soils, both in their natural state and when cultivated. In the light of this information, and with reference to relevant studies and practice in Britain and elsewhere, desirable methods of cultivation and the selection of species for the afforestation of upland heaths are considered.