Excerpts from the executive summary: The critical importance of the first years of life is well acknowledged. Three broad domains of early child development contribute to health, and have a role to play in health equity, across the life course: physical, social/emotional, and language/cognitive. Early child development is influenced by early life factors and experiences that are underlying social determinants of health. At the most intimate level the 'within family' environmental attributes of stimulation, support, and nurturance influence all three key domains of ECD. There are a wealth of studies involving first world, immigrant, and developing country populations showing that nurturing qualities of family environments influence development and can be enhanced through intervention programs involving improved parenting skills, nutritional supplementation, and quality childcare arrangements. Although long-term followup has occurred on only a subset of these studies, the results have been very promising. At the next level of social aggregation, 'neighbourhoods/communities' influence ECD. The key aspects here are safety, cohesion, and the avoidance of ghettoization of poor and marginalized families. The Bernard van Leer and Aga Khan Foundations have both demonstrated that community development approaches to improving child development are feasible and effective in developing country contexts. The challenges here are greater in urban environments than they are in village contexts because urban environments tend to create spatial separation among people from different walks of life and, thus, large differences in the qualities of the neighbourhood environments for children. Nonetheless, taking ECD into account is important when considering the urban aspects of social determinants of health and their relationship to 'sustainable cities'. In the urban context, the concept of spatial organization in the form of 'neighbourhoods' is especially salient. Frequently, the literature finds, inequalities for a variety of outcomes within urban areas are apparent at the neighbourhood-level, in strong part due to inequalities in neighbourhood conditions. The effects of neighbourhood conditions on ECD are a particularly important lens through which neighbourhood organization should be assessed. The development of 'sustainable cities' should explicitly incorporate those neighbourhood conditions which are conducive to providing all children with the fundamental resources for healthy development. At the broadest level of social aggregation, socio-political and program delivery factors make a difference for ECD. Socio-political factors in this context refer to the national wealth and the economic trajectory of a given society; income distribution; patterns of employment and migration; and longstanding attitudes to mothers and children, all of which directly or indirectly influence the conditions under children grow up, live, and learn. At this level of social aggregation the programme delivery factors are much easier to modify than the socioeconomic/structural factors. The 'gold standard' for service delivery around the world would be the local neighbourhood 'hub', through which families could access quality child care (emphasis on stimulation, nutrition, and quality play spaces); infant and family support programs; a conduit to pre and post-natal, primary, and developmental health care services; family literacy programs; and a borrowing library of resources (books and toys) for young children. Examples of such hubs exist in many wealthy countries; in immigrant neighbourhoods; and among Aboriginal communities. Elements of the hub model also exist in developing country programs. In principle, if a supportive community in a developing country has a well functioning hub, children should be able to reach school age at the same level of development as their counterparts in the wealthy world and improve their chances for succeeding in school. Thus, compared with many of the social determinants of health that are deeply embedded in economic processes, we know that most of the social determinants of ECD are relatively easily modifiable. The scope of this document is to integrate knowledge about the different levels of aggregation described above from an international perspective and to discuss the determinants and life course implications of early child development (ECD) at the global level. This review identifies general principles that can guide wealthy and developing countries in improving their children's developmental outcomes during the early years of life and through critical transitions such as entry to school. It presents to the Commission a series of strategic considerations to assist it in planning a successful approach to ECD as a Social Determinant of Health.