In order to operate in an evidence-based fashion, mental health services rely on accurate, relevant, and systematic information. One important type of information is the nature of the problems experienced by recipients of mental health care, and how these problems change over the course of time. Outcome measurement involves the systematic, repeated assessment of aspects of health and illness, either by service providers, service recipients, or both. From outcome measurement clinicians and service recipients achieve a common language whereby they can plan treatment and track progress, team leaders and managers secure a basis to compare their services with others and to promote quality, while policy makers and funders derive evidence of effectiveness. This book will be an essential and practical resource for all members of the mental health clinical team as well as those responsible for establishing or managing services, and directing policy.