Mental disorders in low- and middle-income countries (LAMIC) do not attract global health policy attention. This article is based on a selective review of research on mental disorders in adults in LAMIC since 2001 and recent analyses of disease burden in developing countries. Mental disorders account for 11.1% of the total burden of disease in LAMIC. Unipolar depressive disorder is the single leading neuropsychiatric cause of disease burden. Alcohol use disorders account for nearly 4% of the attributable disease burden in LAMIC. Mental disorders are closely associated with other public health concerns such as maternal and child health and HIV/AIDS. Poverty, low education, social exclusion, gender disadvantage, conflict and disasters are the major social determinants of mental disorders. Clinical trials demonstrate that locally available, affordable interventions in community and primary care settings are effective for the management of mental disorders. Mental health resources are very scarce and investment in mental health is < 1% of the health budget in many countries. The majority of people with mental disorders do not receive evidence-based care, leading to chronicity, suffering and increased costs of care. Strengthening care and services for people with mental disorders is a priority; this will need additional investment in human resources and piggy backing on existing public health programmes. Campaigns to increase mental health literacy are needed at all levels of the health system.