The Child Dental Health Survey, Australia 1999: trends across the 1990s reveals the state of oral health in Australia's school-age children. It includes age-specific and age-standardised measures of dental caries experience and treatment within each State and Territory, and national estimates of these measures for 1999. Australian children experience comparatively low levels of dental caries. However, a minority of children still experience extensive decay and carry most of the burden of this disease. Trends in caries experience are also presented for the period 1990-1999. The findings show that caries experience in both the deciduous and permanent dentitions has changed over time and that in the later half of the 1990s improvements in oral health had ceased. The knowledge of changes in children's oral health can serve as a guide for policy development in order to further improve the oral health of Australian children.