There continue to be enormous changes and advancements in the indexing and retrieval of online health information, fueled by the growth of the Internet and World Wide Web. This has enabled the field of information retrieval, also known as search, to have substantial impact on diverse types of information in areas from consumer health to clinical medicine to genomics. Totally rewritten, this new edition of Information Retrieval: A Health and Biomedical Perspective provides an overview of the theory, practical applications, evaluation, and research directions of all aspects of health and biomedical information retrieval systems. The book is organized into three sections covering basic principles, state of the art systems, and research directions. The book demystifies the jargon and defines where current applications and research systems are heading the field in areas such as digital libraries, linkage to electronic health records, and text mining systems. This book details the technical state-of-the-art and research results in health and biomedical information retrieval. The increasing importance of health information retrieval makes the book an invaluable tool for those involved in this area, such as medical informaticians, computer scientists, library/information scientists, IT developers, and leaders of hospitals, companies, and universities.