The importance of the length of preceding birth intervals for the survival chances of young children has been established, but the debate concerning the causal biomedical or behavioral mechanisms continues. This article uses data from 17 Demographic and Health Surveys to investigate the effect of birth intervals on child mortality: Anthropometry of children, recent morbidity of children, and use of health services are examined in addition to child survival data for children born in the five years before the survey. Various methodological approaches are used to investigate the relative importance of the postulated mechanisms linking birth intervals and child survival. Short preceding birth intervals are associated with increased mortality risks in the neonatal period and at 1-6 months of age, and, to a much lesser extent, at 7-23 months of age. The effects of short birth intervals on nutritional status are rather moderate, and there is a weak relationship with lower attendance at prenatal care services. No consistent relationship exists between the length of birth intervals and other health status or health- service utilization variables. The results indicate that prenatal mechanisms are more important than postnatal factors, such as sibling competition, in explaining the causal nature of the birth interval effect.