We thank the Medical Research Council and the Department of Health for funding the UK Randomised Controlled Trial Registration Project, our colleagues at the UK Cochrane Centre for their support, particularly Inekke Loke, and Hazim Timimi at Update Software.

We thank colleagues at Medical Research Council headquarters who have been helpful throughout: they include Liam O’Toole, Peter Dukes, and Joe McNamara (successive Medical Research Council trials managers); Tony Helm, Jonathan Page and Philip Toms; Sam Balakrishnan, Tracy Simkins, Sandra Iskander, Jill McEachem, and Michelle Bardini.

We thank Claire Vale and Lesley Stewart, Medical Research Council Clinical Trials Unit, both for permitting the use of UK Coordinating Committee on Cancer Research records in the registers we assembled and for assuming ongoing responsibility for the registers.

Within the Department of Health, the NHS research and development programme, and the Chief Scientist Office (Scotland) we thank John Pattison, Chris Henshall, Richard Lilford, Marc Taylor, Kent Woods, Danny Pollard, Alison Spaull, and Jennifer Waterton. We thank Grant Lewison for searching the research outputs database for eligible studies, and Sally Davies, director of research and development for the London region, for funding these searches.

We have been helped by the programme managers for the ongoing national NHS research and development programmes (particularly Lynn Kerridge, National Coordinating Centre for Health Technology Assessment), the time limited national NHS research and development programmes, the regional NHS research and development programmes (particularly Richard Lilford and Ian Goodall), and research units funded through the Department of Health’s centrally commissioned programme, particularly Jon Nicholl at the Medical Care Research Unit (Sheffield), the National Centre for Research and Development in Primary Care, and Sarah Ayers at the National Perinatal Epidemiology Unit.

Leslie Turnberg, director of research at the Association of Medical Research Charities, and Edzard Ernst and Barbara Wider at the University of Exeter helped us to identify which charities should be approached for details of randomised controlled trials. We received information from the following medical research charities: Action Research, Alzheimer’s Society, Arthritis Research Campaign, Ataxia, British Heart Foundation, British Lung Foundation, Chronic Granulomatous Disorder Research Trust, Diabetes UK, Iris Fund for Prevention of Blindness, Little Foundation, Ludwig Institute For Cancer Research, Meningitis Research Foundation, National Asthma Campaign, National Kidney Research Fund, Primary Immunodeficiency Association, REMEDI, Sir Jules Thorn Charitable Trust, Stroke Association, TENOVUS, and William Harvey Research Institute.

Throughout the project, Current Controlled Trials has been helpful beyond the call of duty. We are particularly indebted to Vitek Tracz, Anne Greenwood, Claire Marley, and Hélène Faure.

We thank the following people for their individual contributions to the register: M T Abou-Saleh, R A Anderson, S H Arshad, Antony Arthur, Joan Austoker, D T Baird, Gurvinder Banait, T R E Barnes, Belinda Bateman, Harry Baumer, Jonathan Benger, Richard Bentall, A Bickham, R Bilous, S Bond, Michael Bramble, John Britton, Peter Brocklehurst, Morris Brown, Catherine Bucher, Peter Burney, Christopher Butler, Rona Campbell, D W Chadwick, Usha Chakravarthy, David Chinn, Jose Closs, Rory Collins, Richard Coppin, Kim Cornish, D K Cragg, Francis Creed, Kennedy Cruikshank, Michael H Cullen, Janet Darbyshire, Elaine Davies, Lorraine DeSouza, Paul Dieppe, Mike Doherty, R M L Doran, Peter Draper, Audrey Duncan, Martin Edwards, Diana Elbourne, Roy Farquharson, Astrid Fletcher, Neil French, Jo Garcia, Stephen George, Diana Gibb, Anna Glasier, Catherine Gleeson, Dermot Gleeson, Lucy Goldby, Jonathan Graffy, Kathryn Gray, Julie Greenfield, Michael Griffith, David Gunnell, M P Haggard, Peter Hajek, Diana Harcourt, Richard Harding, Lynda Harper, Robert Harper, Richard Harrington, Timothy Harrison, Nick Heather, Julia Heidstra, Philip Helliwell, Harry Hemingway, Jenny Hewison, Irene Higginson, Kate Hill, Jackie Hill, Sean Hilton, Rury Holman, Peter Hoskin, Allan House, Tim Hughes, Michael Hurley, Eileen Kaner, Sara Kenyon, K T Khaw, Michael King, Ann-Louise Kinmonth, V K Kitchen, Jennifer Klaber Moffett, Rosemary Knight, Justin Konje, Terry Lawrence, Julian Leff, Robert Lewin, S W Lewis, Glyn Lewis, George Lewith, Richard Lilford, R E Mansel, Isaac Manyonda, Valerie Mason, Karen Maughan, Kenneth McColl, Charles McCollum, Sheena McCormack, Victoria McGregor, Lindsay McLellan, Thomas McMillan, T W Meade, Patrick Mesquita, D C Minassian, Paul Moayyedi, A Munro Neville, Lynne Murray, L Mynors-Wallis, Julia Newton Bishop, Patrick O’Dwyer, E M Oliver, J Orford, Charlotte Paterson, Eugene Paykel, Joy Pepper, Lesley Peters, Robert Peveler, Roisin Pill, Susan Plummer, Jeremy Powell-Tuck, Roseanne Pratt, M W Reed, Nicholas Reynolds, Selwyn Richards, Leone Ridsdale, Lisa Riste, Ian Roberts, Michael Roberts, A C Robinson, J Robson, Paul Roderick, Michaela Rodger, Helen Rodgers, Mary Rudolf, P Salmon, Peter Sandercock, Sam Sartain, John Scholefield, R A P Scott, John Scott, Jonathan Scott, Chau Shum, Anita Simonds, Anita Slade, Liam Smeeth, Edmund Sonuga-Barke, Judith Stephenson, Andrew Steptoe, Gregory Stores, Chris Thompson, Paul Thompson, D Thompson, J G Thornton, Peter Todd, W D Toff, Peter Tyrer, M R Vickers, R F Walker, John Wallwork, Susan Walsh, Bronagh Walsh, C P Warlow, J Wellwood, Martin White, Daniel Wight, Kate Williams, Jean Wright, and T Wykes.

We apologise to any organisations and individuals we have inadvertently overlooked.