Many factors affect child and adolescent mortality in high-income countries. These factors can be conceptualised within four domains—intrinsic (biological and psychological) factors, the physical environment, the social environment, and service delivery. The most prominent factors are socioeconomic gradients, although the mechanisms through which they exert their effects are complex, affect all four domains, and are often poorly understood. Although some contributing factors are relatively fixed—including a child's sex, age, ethnic origin, and genetics, some parental characteristics, and environmental conditions—others might be amenable to interventions that could lessen risks and help to prevent future child deaths. We give several examples of health service features that could affect child survival, along with interventions, such as changes to the physical or social environment, which could affect upstream (distal) factors.