To test the hypothesis that children with suboptimal fetal growth have significantly poorer mental health outcomes than those with optimal growth, a population random sample survey of children aged 4 to 16 years in Western Australia in 1993 was conducted. The Child Behavior Checklist (Achenbach 1991a) and the Teacher Report Form (Achenbach 1991b) were used to define mental health morbidity. Survey data for 1775 children aged 4 to 13 years were available for linkage with original birth information. The percentage of expected birthweight (PEBW) was used as the measure of fetal growth. Children below the 2nd centile of PEBW who had achieved only 57% to 72% of their expected birthweight gives their gestation at delivery were at significant risk of a mental health morbidity (OR 2.9, 95% CI 1.18, 7.12). In addition, they were more likely to be rated as academically impaired (OR 6.0, 95% CI 2.25, 16.06) and to have poor general health (OR 5.1, 95% CI 1.69, 15.52).