Longitudinal studies often investigate how a marker that is repeatedly measured in time is associated with a time to an event of interest. An example is prostate cancer studies where longitudinal PSA level measurements are collected in conjunction with the time-to-recurrence. This book provides a full treatment of joint models for longitudinal and time-to-event data. The content is explanatory rather than mathematically rigorous and emphasizes applications. All illustrations put forward are available in the R programming language via the freely available package JM written by the author.