In the early 1970s, comprehensive and authoritative reviews of psychiatric disorders in lowand middle-income countries (LAMI) of Latin America, Sub-Saharan Africa and South East Asia showed that all types of mental disorders were widely prevalent in the developing world. The reviews highlighted the gross neglect of mental disorders in these countries due to a variety of reasons which included pervasive stigma, widespread misconceptions, grossly inadequate budgets and acute shortage of trained personnel. Resulting from these observations, it has commonly been recommended that, in these countries, basic mental health care should be decentralized and integrated with the existing system of general health services. It has also been suggested that a wide range of non-specialist health workers, including primary health care workers, should undertake tasks of mental health care, targeting a selected range of priority mental health conditions. The strategy of integrating mental health into primary care services by training non-specialist health workers was endorsed by the Mental Health Expert Committee of the World Health Organization (WHO) in 1974. More than 25 years later, in 2001, WHO devoted its World Health Report to mental health, focusing on the importance of integrating mental health into primary care. However, since progress in this area was very limited, WHO started a new initiative with the aim of narrowing the wide treatment gap in mental health, aptly titled ‘mhGAP’–‘the mental health Gap Action Programme’, which identifies integration of mental health services into primary care as the most feasible approach to closing the treatment gap in LAMI countries. An ‘Intervention Guide’ consisting of evidence-based, clinical decision-making flow charts, a manual of instructions, training packages and materials and a supervision manual was developed for adoption, adaptation and implementation by LAMI countries.