The study aimed to examine the validity of employing the caries experience of the primary dentition for predicting early caries in the permanent first molar fissures. Subjects consisted of 192 children who were followed for 2 yr, 91 of whom were pursued for a further year, all receiving semiannual check-ups. The caries prevalence in the primary dentition (dmft), excluding incisors, was recorded at baseline, which was the year the children became 6. Fissure caries in the permanent first molars was recorded as being confined to enamel or dentin, based on findings during cavity preparation. The correlation between dmft and the number of intact permanent first molars was -0.368 and -0.337 after 2 and 3 yr observation respectively. When the children were grouped according to their dmft, a statistically significant relationship was found between the dmft and the number of intact molars in each individual. The positive and negative predictive values as well as the sensitivity and specificity of different dmft values were calculated, and the relationship between them illustrated by the use of ROC curves. Even if there are no specific dmft values which seem obviously favorable for the purpose, these data give information relevant in planning for large scale use of fissure sealing in preventing early fissure caries in permanent first molars.