There is a lack of consensus concerning the management of intruded permanent teeth. The objectives of the present study were to determine the prevalence of resorption for intruded permanent teeth and to establish the effect of factors on the timing, prevalence and rate of resorption and to examine the relationship between the timing of onset and the subsequent rate of resorption. Sixty-one intruded permanent incisors treated at the Paediatric Dentistry units in Belfast and Newcastle upon Tyne, during the period 1990-99 with a minimum follow-up period of 1.5 years, were studied. The timing and presence of resorption and its rate of occurrence over time were set as the principal outcomes. There was a significantly earlier onset and higher prevalence of resorption in more severely intruded teeth (P< 0.05). There was also a significant relationship between the degree of apical development and resorption with an increased prevalence in the more fully developed roots (P< 0.001). Resorption was detected significantly earlier in teeth with higher rates of resorption (P< 0.05). However, the treatment method did not significantly affect the prevalence or rate of resorption. In conclusion, the occurrence of root resorption after intrusive trauma appears to be related to the severity of the original injury and the stage of root development rather than the repositioning procedure.