We call for the global health community, governments, donors, multilateral agencies, and other mental health stakeholders, such as professional bodies and consumer groups, to scale up the coverage of services for mental disorders in all countries, but especially in low-income and middle-income countries. We argue that a basic, evidence-based package of services for core mental disorders should be scaled up, and that protection of the human rights of people with mental disorders and their families should be strengthened. Three questions are critical to the scaling-up process. What resources are needed? How can progress towards these goals be monitored? What should be the priorities for mental health research? To address these questions, we first estimated that the amount needed to provide services on the necessary scale would be US$2 per person per year in low-income countries and $3-4 in lower middle-income countries, which is modest compared with the requirements for scaling-up of services for other major contributors to the global burden of disease. Second, we identified a series of core and secondary indicators to track the progress that countries make toward achievement of mental health goals; many of these indicators are already routinely monitored in many countries. Third, we did a priority-setting exercise to identify gaps in the evidence base in global mental health for four categories of mental disorders. We show that funding should be given to research that develops and assesses interventions that can be delivered by people who are not mental health professionals, and that assesses how health systems can scale up such interventions across all routine-care settings. We discuss strategies to overcome the five main barriers to scaling-up of services for mental disorders; one major strategy will be sustained advocacy by diverse stakeholders, especially to target multilateral agencies, donors, and governments. This Series has provided the evidence for advocacy. Now we need political will and solidarity, above all from the global health community, to translate this evidence into action. The time to act is now.