The aim of the present investigation, which is a continuation and extension of a previous published pilot study [Forensic Sci. Int. 129 (2002) 110], was to calculate the chronological age of an individual based on the dental developmental stages of third molars (so-called wisdom teeth). The evaluated material consisted of 2513 orthopantomograms (OPG's) of patients all of Belgian Caucasian origin between 15.7 and 23.3 years. The sample of OPG's was scored by two observers who were calibrated for intra- and interobserver reliability by means of kappa statistics. The kappa statistics revealed a strong agreement between the intra- and interobserver measurements. Further statistical analysis was performed in order to obtain multiple regression formulae for dental age calculation with the chronological age as the independent variable and the third molar developmental stages as dependent variables. Both for males and females a significant Pearson correlation coefficient was noticed for contralateral third molars, a smaller less significant one for the antimeres. For the application of the regression formulae one has to take into consideration the gender, the location and number of wisdom teeth. Probabilities for an individual to be older than 18 years were also calculated in case of fully developed wisdom teeth.