Longitudinal data on tooth emergence were collected from birth to 18 years from 212 randomly selected Swedish urban children. At 18 years, 76 per cent (160/212) of the original subjects were examined. All deciduous teeth except the mandibular second molar emerged earlier in boys than in girls, but the sex difference was only statistically significant (p less than 0.05) for the maxillary laterals and mandibular canines. All permanent teeth emerged significantly earlier in girls than in boys, the sex difference being 2.5 to 14 months.