The prevalence and yearly incidence of traumatic tooth injury between 1 and 16 years of age were studied in a cohort of 16-year-olds, born in 1975, and residing in the County of Västerbotten, northern Sweden. The study comprised 3007 dental records from the public dental health service. The general distribution was 50.3% girls and 49.7% boys. The records showed that 35% of the children on one or more occasions had sustained injury to their primary or permanent dentition. The frequency was nearly twice as high for boys (64%) as for girls (36%). Twenty-five percent of the 16-year-olds had met with tooth injury more than once and this group consisted predominantly of boys. The incidence of injury episodes to primary and permanent teeth was 28 per 1000 per year. The boys had sustained trauma to their teeth most frequently when they were 4 years of age and between the ages of 8 and 11. This was also true for girls at 4 and at 9 years of age, although less evidently so. In the primary dentition, the majority of dental injuries had affected the supporting tissue of the maxillary incisors. In the permanent dentition, 75% of the traumatised teeth were upper incisors. Fractures of varying severity constituted 60% of all registered diagnoses in this dentition, followed by subluxation (19%) and concussion (11%).