A second nationwide survey in 2004 aimed to describe the oral health status of children in the Islamic Republic of Iran and to provide baseline data for the organization and evaluation of the national oral health promotion programme. WHO pathfinder sampling procedures were used to select representative samples of children aged 3, 6, 9 and 12 years. Data on decayed/missing/filled teeth, caries-free rates and treatment needs were collected from 18 946 children using WHO standard methods. The mean dmft/DMFT indices were 1.9/– for 3-year-olds, 5.0/0.2 for 6-year-olds, 3.6/0.9 for 9-year-olds and 0.6/1.9 for 12-year-olds. Significant differences in dental caries prevalence were found according to sex, province, urban/rural residence, family income and parents’ level of education.