This authoritative textbook is designed for use by final year undergraduates, those engaged in training for both clinical and health psychology, and practitioners. It combines elements of both clinical and health psychology in one volume. The book has five key themes: the causes of health and illness; psychological factors influencing the understandings of health, illness and health-related behaviour choice; the theory and application of psychological principles in facilitating individual behavioural and emotional change; the role of psychologists within the wider hospital system; and the role of psychology in population-based health promotion. This text integrates psychological theory with the practice of health and clinical psychology in the hospital and in the broader context of health care. It considers both clinical interventions and those of a non-clinical nature that also impact on patients and health-care workers. In doing so, it addresses the developing curriculum for health psychologists' professional training as well as the more established role of clinical psychologists.