Socio-economic inequalities in adult and child health in Australia have been an issue of national concern. While a large body of data has discussed adult health, there have been relatively few Australian reports of socio-economic inequalities in child health. This occurs in a context where there have been increases in the proportion of Australian children living in poverty and where there has been an increased interest in child developmental delay as an indicator of child health status. This paper reports the result of a longitudinal study of pregnancy outcomes and one indicator of child health, namely child developmental delay. Three indicators of socio-economic status (chronic socio-economic disadvantage, mother's education, family income) were used to predict child developmental delays observed some 5 1/2 years after the study commenced. Mothers who had the lowest socio-economic status (using any of the indicators) had substantially higher rates of children manifesting developmental delays.