The aim of the present investigation was to study the prevalence of approximal caries lesions and fillings in posterior teeth at 15 years of age in a prospectively followed Swedish population (n = 568), with special reference to their caries experience at the age of 3 years. Only approximal surfaces were recorded, since all children in the Community of Jönköping have had fissure sealing performed on all caries-free permanent molars. At 15 years of age, the mean number of approximal tooth surfaces with initial caries lesions (Dia), manifest caries lesions and fillings (DmFa) and total caries experience and fillings (Di + mFa) – recorded on bitewing radiographs – was 2.78 , 0.45 and 3.23, respectively. One third of the adolescents had no approximal caries or fillings; the Dia constituted 86% of the Di + mFa. Children with manifest caries at 3 years of age had a higher risk of developing approximal caries in their permanent teeth than caries-free children at the same age (41 vs. 17%). Furthermore, children who were caries-free at 3 years of age were more likely to remain caries-free at 15 years of age compared to children with manifest caries (37 vs. 17%). All these differences were statistically significant (p < 0.001). Additionally, early childhood caries experience (developed before 3 years of age) had a greater predictive value than late childhood caries experience (developed between 3 and 6 years of age) concerning approximal caries at 15 years of age.