Intended for healthcare professionals

Research Methods & Reporting

Developing and evaluating complex interventions: the new Medical Research Council guidance

BMJ 2008; 337 doi: (Published 29 September 2008) Cite this as: BMJ 2008;337:a1655
  1. Peter Craig, programme manager1,
  2. Paul Dieppe, professor2,
  3. Sally Macintyre, director3,
  4. Susan Michie, professor4,
  5. Irwin Nazareth, director5,
  6. Mark Petticrew, professor6
  1. 1MRC Population Health Sciences Research Network, Glasgow G12 8RZ
  2. 2Nuffield Department of Orthopaedic Surgery, University of Oxford, Nuffield Orthopaedic Centre, Oxford OX3 7LD
  3. 3MRC Social and Public Health Sciences Unit, Glasgow G12 8RZ
  4. 4Centre for Outcomes Research and Effectiveness, University College London, London WC1E 7HB
  5. 5MRC General Practice Research Framework, London NW1 2ND
  6. 6Public and Environmental Health Research Unit, Department of Public Health and Policy, London School of Hygiene and Tropical Medicine, London WC1E 7HT
  1. Correspondence to: P Craig peter{at}
  • Accepted 23 August 2008

Evaluating complex interventions is complicated. The Medical Research Council's evaluation framework (2000) brought welcome clarity to the task. Now the council has updated its guidance

Complex interventions are widely used in the health service, in public health practice, and in areas of social policy that have important health consequences, such as education, transport, and housing. They present various problems for evaluators, in addition to the practical and methodological difficulties that any successful evaluation must overcome. In 2000, the Medical Research Council (MRC) published a framework1 to help researchers and research funders to recognise and adopt appropriate methods. The framework has been highly influential, and the accompanying BMJ paper is widely cited.2 However, much valuable experience has since accumulated of both conventional and more innovative methods. This has now been incorporated in comprehensively revised and updated guidance recently released by the MRC ( In this article we summarise the issues that prompted the revision and the key messages of the new guidance.

Summary points

  • The Medical Research Council guidance for the evaluation of complex interventions has been revised and updated

  • The process of developing and evaluating a complex intervention has several phases, although they may not follow a linear sequence

  • Experimental designs are preferred to observational designs in most circumstances, but are not always practicable

  • Understanding processes is important but does not replace evaluation of outcomes

  • Complex interventions may work best if tailored to local circumstances rather than being completely standardised

  • Reports of studies should include a detailed description of the intervention to enable replication, evidence synthesis, and wider implementation

Revisiting the 2000 MRC framework

As experience of evaluating complex interventions has accumulated since the 2000 framework was published, interest in the methodology has also grown. Several recent papers have identified limitations in the framework, recommending, for example, greater attention to early phase piloting and development …

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