The aim of the present study was to evaluate fissure sealing of permanent teeth in children during a 10 year period. All completely erupted caries-free permanent first molars were sealed in 6 to 9 year-old children forming the patient population of one of the authors. 758 sealed fissures were controlled and followed up in the study. The fissure sealant material Delton was used and the treatments were performed according to the manufacture's recommendations. The sealings were controlled once a year and the follow-up period varied from one to 10 years. After 8 years, about 80 per cent of the sealed fissures showed total sealant retention and no caries. Another 16 per cent of the sealed occlusal surfaces showed partial retention and no caries. After 10 years only 5.7 per cent of the sealed occlusal surfaces showed caries or restorations. The results underline that fissure sealing is an effective treatment and has a low failure rate.