Objective: To standardise a complex intervention by defining the characteristic (specific) components of treatment for a randomised controlled trial of acupuncture as an intervention for individuals who have been diagnosed with depression using a consensus method. Methods: A nominal group technique was used. Potential components of the acupuncture intervention were generated from the literature, experts and participants. These were categorised as constant or variable, the latter including active management techniques (such as providing relevant explanations), auxiliary techniques (such as auricular acupuncture), and other aspects of patient care (such as offering life-style and dietary advice), all of which were underpinned by defined theoretical frameworks. Participants were selected on the basis of their experience and training, to encompass a diverse range of styles of traditional acupuncture practice in the UK, and all rated components in two rounds. Results: Fifteen practitioners rated 52 variable components in the first round and 55 in the second. There was group support for 16 active management components, three auxiliary techniques and five areas of life-style support, all driven by eight theoretical diagnostic and treatment frameworks. For the 39 components that were rated twice, group support increased between rounds from 75 to 79% (z=-2.2, p=0.03), while the absolute average deviation from the median dropped from 1.04 to 0.83 (z=-2.5, p=0.011). Conclusion: Standardising the characteristic components of a complex intervention for a randomised controlled trial of acupuncture for depression using a consensus approach is feasible. The method can be generalised to other clinical situations and other treatment modalities. Crown Copyright (c) 2006 Published by Elsevier Ltd. All rights reserved.