The lengths of molar, premolar and canine teeth were determined from orthopantomograms collected in the Nymegen Growth Study. In this Mixed-Longitudinal Interdisciplinary Investigation orthopantomograms were taken every six months from 486 children, covering the age range 4-14 years. A statistically relevant number of mixed-longitudinal data were found for the canines and premolars in the maxilla and for the canines, premolars and molars (except third molars) in the mandible. These data on tooth formation expressed in age reference charts provide useful information for research purposes as well as for orthodontic diagnosis and treatment planning.