The iodine status of children between the ages of 5 and 15 years has been routinely assessed in many countries, but few studies have examined iodine status in pre-school children. We conducted a cross-sectional study of pre-school children living in Adelaide, South Australia, between 2005 and 2007. Children 1-5 years old were identified using a unique sampling strategy to ensure that the study population was representative. A 3-day weighed diet record, a blood sample and a urine sample were obtained from each child. The median urinary iodine concentration (UIC) of the children (n=279) was 129μgL-1, indicating iodine sufficiency (normal range: 100-199μgL-1), but 35% of the children had a UIC<100μgL-1. The median thyroglobulin concentration of children (n=217) was 24μgL-1 and thyroglobulin concentration declined with increasing age (P=0.024). The mean daily iodine intake was 76μg. The intake of iodine was lower than expected and highlights difficulties in accurately assessing iodine intakes. Further studies are needed to monitor dietary changes and iodine status in this age group since the implementation of mandatory fortification of bread with iodised salt in Australia in 2009.