This section can only present a brief synopsis of selected issues regarding clinical trials. These chapters are not intended as a primer on how to conduct clinical trials, but rather a discussion on some of the main issues one will consider in the planning, conducting, and interpretation of data from clinical trials. Chapter 59 is a broad review of clinical trials, but the other chapters in this section are on more specialized topics, and represent an “intermediate” level of principles, practices and issues. The book Guide to Clinical Trials (Spilker 1991) is a far more comprehensive presentation of clinical topics and includes many introductory level chapters. In many ways, the chapters that follow in this section are intended as a supplement to that book, which also focused on the principles and issues involved in clinical trials. Readers are referred to that text for more extensive discussions on many topics not covered in this book. Some of the newer technologies (e-based clinical trials) and topics (clinical trial registries and directories) that have evolved since Guide to Clinical Trials was published are one of the focuses of this section.