Objective: To analyse the relationship between caries determinants in early childhood and caries prevalence in proximal surfaces in adolescents at the age of 15 years. Methods: The present longitudinal study is part of a series of surveys of oral health in 671 children followed from 1 to 15 years of age. Data were selected from examinations, interviews and questionnaires at 1, 3 and 6 years and bitewing radiographs at 15 years of age. Uni- and multivariable logistic regression analyses were performed to identify caries-related determinants. The outcome variable was carious lesions and fillings (DFa) in approximal tooth surfaces at 15 years of age. Statistical comparisons were made between caries-free teenagers, DFa = 0 and teenagers with DFa > 0, DFa 4 and DFa 8, respectively. Results: In the final logistic regression analyses, caries experience at 6 years and mother's self-estimation of her oral health care as being less good to poor remained statistically significant and were related to caries in all three caries groups (i.e. DF > 0, 4 and 8) at 15 years of age. The consumption of sweets at 1 year remained statistically significant, with a caries experience of DF 4 and 8. The variables 'parents born abroad' and female gender were statistically significantly associated with DFa 4 and DFa 8, respectively. Furthermore, infrequent toothbrushing habits at 3 years of age and failure to attend the examination at 1 year were statistically significantly associated with caries at 15 years in the univariable analyses. Conclusion: Early caries experience, consumption of sweets at an early age and mother's self-estimation of her oral health care as being less good to poor are associated with approximal caries in adolescents. The study indicates that caries determinants identified during early childhood have a strong impact on approximal caries in adolescence.