The first aim of this study was to collect a large sample of radiographs from children with congenitally missing teeth (CMT) in the primary dentition and to analyse the local relationship between agenesis of a primary tooth and the presence/absence of its permanent successor. The second aim was to compare, in the same sample, the pattern of agenesis in the primary dentition with the developmental pattern seen in the permanent dentition. 124 dentists from 72 municipalities contributed to the investigation of a total of 213 children. The dentists were asked to lend existing radiographic material from patients with agenesis in the primary dentition. The analysis of the local occurrence of agenesis showed that agenesis of a primary incisor was often but not always followed by agenesis of the succedaneous tooth. In the molar region, agenesis of a primary tooth was in all cases but one followed by agenesis of the succedaneous tooth. Comparison of the pattern of CMT in the primary dentition with the pattern of tooth presence/absence in the permanent dentition in a group of 33 patients, for whom complete radiographic material was available showed that agenesis always occurred in the permanent dentition and that the pattern of agenesis in the permanent dentition differed from that in the primary dentition. Incisors were most frequently missing in the primary dentition and premolars in the permanent dentition. The number of congenitally missing teeth was substantially larger in the permanent dentition that in the primary dentition. Also, permanent teeth that are very rarely congenitally missing were missing in this sample, characterized by the occurrence of agenesis in the primary dentition.