This thought-provoking book discusses the use of statistics in randomized clinical trials. Its aim is two-fold: firstly, it presents a clear account of the design and analysis of experiments in this setting which stresses the foundational issues involved. Secondly, the book seeks to develop the specific tools of analysis which can be derived from Neyman's model of restricted tests. The book is based on the author's many years of experience of clinical trials. Throughout, examples are used from a variety of types of study. As a result, all statisticians and research scientists who work on clinical trials will find this presentation clear and accessible, and very relevant to their own research interests.