In the course of medical research, data on the time to the occurrence of a partic of a patient, are frequently encountered. Such data ular event, such as the death are generically referred to as survival data. However, the event of interest need not necessarily be death, but could, for example, be the end of aperiod spent in remission from a disease, relief from symptoms, or the recurrence of a particular condition. Although there are a number of books devoted to the analysis of sur vival data, this book is designed to meet the need for an intermediate text which emphasises the application of the methodology to survival data arising from med ical studies, which shows how widely-available computer software can be used in survival analysis, and which will appeal to statisticians engaged in medical re search. This book is based on a course on the analysis of survival data from clinical trials which has been given annually by the Statistical Services Centre ofthe Department of Applied Statistics, University of Reading, since 1986. Although it is written primarily for those working as statisticians in the pharmaceutical industry and in medical research institutes, much of the text should be accessible to numerate scientists and clinicians working alongside statisticians on the analysis of their own data sets. This book could also be used as a text to accompany undergraduate and postgraduate courses on survival analysis in universities and other institutes of higher education.