This book discusses the statistical analysis of clustered survival data. Such data are encountered in many scientific disciplines including human and veterinary medicine, biology, epidemiology, public health and demography. A typical example is the time to death in cancer patients, with patients clustered in hospitals. Frailty models provide a powerful tool to analyse clustered survival data. In this book different methods based on the frailty model are described and it is demonstrated how they can be used to analyse clustered survival data. Worked-out examples based on real data are used to show how particular frailty models can be fitted and to explain how the results should be interpreted. All programs used for these examples are available on the Springer website.