Bradford Hill has defined a clinical trial as "A carefully and ethically designed experiment with the aim of answering some precisely framed question" [1]. This definition specifies a careful design and requires the provision of adequate controls. Random allocation of treatments to subjects is important to ensure is entitled that the treated and control groups are similar. Therefore this book Randomised Controlled Clinical Trials. We can define a randomised controlled trial by rewriting Bradford Hill's definition as follows, "A carefully and ethi­ cally designed experiment which includes the provision of adequate and ap­ propriate controls by a process of randomisation, so that precisely framed questions can be answered. " I am a firm advocate ofRandomised Controlled Clinical Trials but intend to give a balanced view of the advantages and disadvantages of these ethical experiments. This book is directed primarily at the medical research worker, although certain chapters may find a wider application. When discussing a randomised controlled trial, it is neither practicable nor desirable to divorce theory from practice, however the first ten chapters con­ centrate mainly on theory, and the remainder focus on practice. The segment on trial design is followed by sections on writing the protocol, designing the forms, conducting the trial, and analysing the results. This book is meant to serve both as a reference manual and a practical guide to the design and performance of a trial.

1. Introduction.- 2. The history of controlled trials.- 3. Ethical considerations.- 4. The objectives of a randomised controlled trial.- 5. Validity of the results.- 6. Recruitment of subjects.- 7. How to ensure that the control and treated patients are similar in all important respects.- 8. How to ensure that the results are free of bias.- 9. The variability of results.- 10. How many subjects are required for a trial?.- 11. Different trial designs.- 12. Writing the protocol.- 13. Information to be collected during a trial.- 14. The conduct of the trial.- 15. Analysis of the trial results.- 16. The evaluation of subjective well-being.- 17. Early trials on new drugs.- 18. The detection of adverse drug reactions.- 19. Failure to accept the results of randomised controlled trials.- 20. The advantages and disadvantages of randomised controlled trials.- 21. References.