Gender, in a given society at a specific time and place, is of critical importance to young child survival and development (YCSD). Effective YCSD programmes must respond to how gender influences the character of social norms, processes of decision-making, division of labour and differences in access to resources among girls, women, boys and men. In these ways, gender determines exposure to risks, programme responses and outcomes at household, community, service delivery system and policy levels. Gender matters because biological differences create different vulnerabilities, e.g., the increased nutritional needs and increased susceptibility to malaria of pregnant women. Gender matters because social norms can create inequitable burdens on different groups, for instance when girls are taken out of school to help care for sick relatives or to queue for their families’ water supply. Moreover, gender matters even when no apparent difference in outcomes between girls and boys exists, for instance when the boys and girls of highly educated mothers are more likely to get immunised than the boys and girls of mothers with little education.