The purpose this study is to elaborate on fertility differentials, based on the average number of children ever born or life births per woman. According to survey results from Indonesia and other developing countries, the relationship between fertility and economic class does not show a consistent pattern. In some studies these two variables indicated a negative association, but in others the relationship was positive. It is interesting that despite very different socio-economic conditions between Mojolama and Kedung Miri, two of the three dukuh (hamlets) in Sidoarjo, the fertility levels were nearly the same. However, the fertility levels in Mojolama and Kedung Miri were low compared to the fertility in the other provinces of Java.