Early intervention (EI) is arguably the single most important advance in mental health care of the past decade. In terms of all-time advances in mental health care delivery, EI is up there with the consumer, family, recovery, and human rights for psychiatric disability movements, person-centred and holistic integrated services, effective psychotropic medications and psychotherapeutic interventions, evidence-based psychosocial interventions and mobile assertive community-centred service delivery systems. EI represents a key shift in both theoretical standpoint and service delivery, and marks an end to the first era of community psychiatry - where we set up 'accessible' clinical structures by locality, and patients were expected to adapt to these. With EI, practitioners reconfigure how they work to engage, negotiate and agree interventions support and care with their ser- vice users. From a general practitioner (GP) perspective, some modern community mental health teams (CMHTs) have 'raised the bar' to focus only on those with severe mental illness (SMI), now implicitly or formally defined as established psychotic disorders. Many CMHTs decline people in crisis or in the early stages of illness: by the time their referral is accepted later on, engagement is harder and many interventions have a reduced efficacy. Like all useful ideas, EI is a simple one and has instant appeal to people in early stages of illness (crucially often before insight is lost) and to their families. Key clinicians, notably GPs and mental health professionals also have a strong self-interest in designing and supporting efficient EI services. It is both self-evident to them, and increasingly evident from emerging studies, that such timely approaches could save much harder and longer clinical endeavour further down the track. We list the key pioneers later (Chapter 27), many of whom have contributed to this book. Their work, along with impressive citations at the end of each chapter, should persuade readers new to EI that this will be a key component of the twenty-first century mental health care. This book's main aim is to affirm for every clinician, every purchaser of services and other interested parties the high value of EI in most care settings from cradle to grave.