The associations between birth interval and a range of child health outcomes were examined in a population-based cohort of approximately 3500 urban Brazilian children. The effects of several socioeconomic and maternal confounding factors were controlled for in the analyses. Children born after shorter birth intervals (less than 18 and 18 through 23 months) were disadvantaged with respect to most of the health outcomes when compared with children born after intermediate birth intervals (24 through 35, 36 through 47, and 48 through 71 months). Effects were particularly marked for birth weight, postneonatal mortality, and anthropometric status at mean age 19 months. Children born after a long birth interval (greater than 71 months) also showed some disadvantage for birth weight, perinatal mortality, and infant mortality. However, this group experienced lower risks of hospitalizations during the first 19 months of life and better anthropometric status at mean age 19 months. This study provides data that are scarce from such settings and contributes to the quantification of associations between birth spacing and child health. This information is important in the planning of appropriate intervention strategies.