Using data from Mexico's Demographic and Health Survey, the authors examine the effects of breast-feeding and the pace of childbearing on early childhood mortality in a sample of 2,665 children born between 1982 and 1986. From a family planning perspective, they seek to assess the impact that changes in childbearing patterns and associated changes in breast-feeding patterns may have on infant and childhood mortality. To examine likely interactions between family planning, breast-feeding, and mortality, an integrated model was applied that simultaneously considered a range of other variables. The results suggest that the effects of improved birth spacing and maternal age at delivery associated with family planning are powerful enough to cause 20-40% reductions in infant mortality. However, the effects of reduced breast-feeding associated with family planning are great enough to offset more than 60% of these benefits. Limitations of the model make it necessary to emphasize that all of these conclusions need to be accepted with caution.