Douglas fir plays a particular role in the production of quality timber and is also important for other multipurpose forestry uses. Due to the extent of its natural range in Pacific north-west America, a range of material from natural populations and tree improvement programmes has been evaluated in field trials to identify the most well-adapted sources for planting in Great Britain. This publication summarises the results from over half a century of research. The growth and production data have been used to produce suitability maps which can assist forest managers in their decisions on the choice of seed origin for planting. The publication is recommended reading for forest managers, advisors and researchers alike - as well as readers interested in the development and use of species from the Pacific Northwest in British forestry.