This study describes the frequency of hypodontia among all the children of the same age group in a Norwegian municipality and reports variations of some dimensions of the dentition associated with hypodontia. Congenitally missing permanent teeth, not including third molars, were found in 7.1 per cent of the material at age seven, and in 6.6 per cent at age nine. The difference seemed to be due to insufficient mineralization of the second lower premolars in boys at age seven. The frequency of hypodontia per se was a little higher in girls than in boys, and the girls were missing more teeth per individual. Neither the dental arch width nor the mesiodistal diameter of the teeth were significantly different in the hypodontia group compared to a control group without hypodontia.