About four out of five people in low- and middle-income countries who need services for mental, neurological and substance-use conditions do not receive them. Even when available, the interventions often are neither evidence-based nor of high quality. WHO recently launched the mental health Gap Action Programme (mhGAP) for low- and middle-income countries with the objective of scaling up care for mental, neurological and substance-use disorders. This mhGAP Intervention Guide has been developed to facilitate mhGAP-related delivery of evidence-based interventions in non-specialized health-care settings. There is a widely shared but mistaken idea that all mental health interventions are sophisticated and can only be delivered by highly specialized staff. Research in recent years has demonstrated the feasibility of delivery of pharmacological and psychosocial interventions in non-specialized health-care settings. The present model guide is based on a review of all the science available in this area and presents the interventions recommended for use in low- and middle-income countries. The "Intervention Guide" includes guidance on evidence-based interventions to identify and manage a number of priority conditions. The priority conditions included are depression, psychosis, bipolar disorders, epilepsy, developmental and behavior disorders in children and adolescents, dementia, alcohol-use disorders, drug-use disorders, self-harm/suicide and other significant emotional or medically unexplained complaints. These priority conditions were selected because they represent a large burden in terms of mortality, morbidity or disability, have high economic costs, and are associated with violations of human rights. The "Intervention Guide" has been developed for use in non-specialized health-care settings. The guide is aimed at health-care providers working at first- and second-level facilities. These health-care providers may be working in a health center or as part of the clinical team at a district-level hospital or clinic. They include general physicians, family physicians, nurses and clinical officers. Other non-specialist health-care providers can use the "Intervention Guide" with necessary adaptation. The first-level facilities include the health-care centers that serve as first point of contact with a health professional and provide outpatient medical and nursing care. Services are provided by general practitioners or physicians, dentists, clinical officers, community nurses, pharmacists and midwives, among others. Second-level facilities include the hospital at the first referral level responsible for a district or a defined geographical area containing a defined population and governed by a politico-administrative organization, such as a district health management team. The district clinician or mental health specialist supports the first-level health-care team for mentoring and referral.The "Intervention Guide" is brief so as to facilitate interventions by busy non-specialists in low- and middle-income countries. It describes in detail what to do and emphasizes the importance of non-specialist health-care providers being trained in using the mhGAP Intervention Guide for assessing and managing people with mental, neurological and substance-use disorders.