Purpose: The aim of the present study was to analyse the association between socioeconomic and behavioural factors and the presence of active non-cavitated caries lesions in 12-year-old adolescents in Piracicaba, São Paulo, Brazil. Materials and Methods: A cross-sectional study was carried out in 1001, 12-year-old adolescents who were selected by the cluster sampling method. A modified version of the World Health Organization criteria for identifying lesions including white lesions (WL) in enamel was used. Information on behavioural and socioeconomic factors was obtained using a semi-structured questionnaire. The outcome variables were DMFS, DMFS+WL and WL. The data obtained were analysed using the chi-square test and a logistic regression model. Results: The mean DMFS was 1.87 (SD = 3.05) and DMFS+WL was 2.27 (SD = 3.66). The logistic regression model showed that income was statistically significantly associated with DMFS, DMFS+WL and WL, whereas educational level of the father, number of residents in the house and number of dental visits were associated with DMFS and DMFS+WL. The onset of toothbrushing was associated with WL. Conclusions: The present study showed that economic factors are associated with all stages of caries development. In addition to these factors, family size, number of dental visits, educational level of the father and onset of toothbrushing could be considered markers of dental health risk. Keywords: behaviour, non-cavitated caries, oral epidemiology, socioeconomic conditions