Fertility and child mortality are supposed to have a two-way relationship. First, women who experience more child deaths go on to bear more children compared to women whose children survive. Second, the risk of children dying is higher among women who have been pregnant more times. Using a unit record data set from South Africa this paper examines the inter-relationship between fertility and child mortality. We use a disaggregated measure of child mortality, which allows us to account for still births and child deaths before the age of 1 and between the ages 1-5 separately, thereby allowing us to isolate the different factors that affect child mortality at the different stages. To the best of our knowledge this particular disaggregation has not been used before. Our estimation results indicate that there is a significant two-way relationship between fertility and child mortality. We also find that improvements in mother's education significantly reduce both fertility and child mortality.