Forensic psychiatry services have grown and become more complex in structures, processes and pathways. Legacy customs, practices and changing policy are now organised into formal models of care. These are written accounts of how a health service is delivered, outlining best practice and services for patients progressing through the stages of their condition and the care and treatment available. This article explores the four key elements of a model of care: goals; pathways and processes; treatment programmes; and systematic evaluation. It describes the most common model of care in forensic services, which builds on structures of stratified therapeutic security. It also considers variations on this basic or standard model matched to needs arising from the complex interrelationship with other parts of the mental health service for the population served and with criminal justice, primary care and physical health, housing and welfare agencies.