INTRODUCTION:Recent evidence indicates that the oral health for children in Timor-Leste is deteriorating, with 40% of school children experiencing toothache during 2014. Timorese have easy access to sugar, poor food security and lack of water fluoridation, all of which exacerbate the risk of dental caries. A lack of quality epidemiological data is available to confirm anecdotal information of high caries rates in rural and remote Timor-Leste. Such data are required to inform oral health issues and health policy at both the local and national levels. This study investigated the caries status and potential risk factors among primary school children in the rural Aileu municipality of Timor-Leste. The objectives of this study were to determine caries prevalence and experience, the status (active/arrested) of existing caries lesions and associations between dental caries and potential risk factors, among primary school children in the Aileu municipality, Timor-Leste. METHODS:This study analysed secondary data. De-identified data for this analysis were obtained from North Richmond Community Health (NRCH), Melbourne, Australia. North Richmond Community Health (NRCH) has been working with the Friends of Aileu (a government-to-government partnership between an Australian local government area and the municipality of Aileu) to improve the oral health of school children in the municipality of Aileu. NRCH conducts an outreach school-based oral health promotion program, called Kose Nehan, at six primary schools in the Aileu municipality. Caries was diagnosed using the International Caries Detection and Assessment System (ICDAS) and reported using the decayed, missing and filled teeth (DMFT/dmft) index. Examiners were trained and calibrated. A brief interviewer-administered questionnaire was used to capture information on child oral hygiene and diet behaviours. For the analysis, dental caries was defined as 'any caries lesions' (ICDAS caries codes 1-6). Descriptive and inferential analyses were conducted using STATA 14. Multivariable logistic regression analysis predicting the odds of dental caries (yes/no) was used to determine independent associations between the exposures and the outcome. RESULTS:Data were analysed for 685 children. In the primary dentition, the overall prevalence of caries was 64% and the mean dmft score was 2.74 (standard deviation (SD) 3.08). In the permanent dentition, the overall prevalence was 53% and the mean DMFT score was 1.74 (SD 2.46). Overall, approximately 84% of caries lesions were identified as being active. The multivariable regression analysis did not identify independent predictors of caries. CONCLUSION:Dental caries was highly prevalent among this population and urgent action is required to reduce the population burden of this disease. Malnutrition, which was not measured for this study, is highly prevalent among children in Timor-Leste and could explain the high caries rates in this population. The effect of malnutrition on dental caries and vice-versa needs further investigation. Programs and policies are urgently needed for oral health promotion and also the prevention and management of dental caries in Timorese children. These strategies should also address the urgent need for emergency dental services aimed at pain relief, first aid for oral infections and restorations, given the high prevalence of advanced disease in this child population.