IntroductionGood mental health is an integral component of population health and wellbeing and contributes to the functioning of individuals, families, communities and the social and economic prosperity of society [1,2]. Promoting mental health and wellbeing will deliver improved health and social outcomes for the general population and for people with mental health problems. Despite the recognition of the importance of mentalhealth, it remains a neglected aspect of public health, especially in low- and middle-income countries (LMICs). People living in poverty and other forms of social disadvantage bear a disproportionate burden of mental disorders [3-5]. Addressing the social determinants of mental health is central to the global development agenda and affects progress towards the achievement of the Millennium Development Goals [6-8]. Mentalhealth promotion and prevention needs to be integrated into population health improvement and development strategies, together with primary and secondary health care delivery .This paper provides a briefing for policy and decision-makers on the evidence for mental health promotion and primary prevention interventions that can be implemented and sustained at a reasonable cost, whilst generating clear health and social gains in the population. Evidence fromhigh, middle and low income countries clearly show that there are effective and feasible interventions for promoting mental health and preventing mental ill-health that represent a cost-effective use of resources and a strong case for policy investment [1,2,11-14]. This paper provides a guide, based on best available evidence, to support decision making in identifying priority areas and “best buys” for implementation.