There is a consistent association between unfavourable socio-economic circumstances and oral health. Although the effects of poor social circumstances in childhood are known to have lasting influences on general health, there is little information on their effects regarding chronic oral diseases. Objective: To assess the relationship between oral health status and socio-economic circumstances at two different periods of adolescents' life. Methods: A two-phase cross sectional study was carried out in Brazil. In Phase I, 652 13-year-olds were clinically examined and interviewed. In the second phase, 311 families were randomly selected for in-depth interviews. Information was collected on several indicators of socio-economic circumstances, family related variables, school grade level, and oral health behaviour, at two different life stages, at birth and at 13 years of age. The outcome variable was oral health status at the age of 13. It was constructed by counting the worst scores of DMFT, gingival bleeding, calculus and dental plaque. The data analysis used stepwise logistic regression. Results: The response rates for phases I and II were 85% and 94%. Boys, those at a lower grade level at school for their age, and those who experienced high levels of material deprivation at birth and at the age of 13 were more likely to have high levels of oral diseases; the odds ratios were 4.12 (1.86–9.16), 2.41 (1.01–5.76) and 4.61 (1.30–16.3), respectively. Conclusion: Brazilian adolescents experiencing adverse socio-economic circumstances at birth and at the age of 13 had high levels of oral diseases.