Aim: The aim of this study was to investigate the methods used to identify national mean DMFT scores for 12-year-old children in all the Member States of the European Union and European Economic Area, and in 11 other European countries. Methods: The most recent national mean DMFT scores were accessed from the World Health Organisation Oral Health CAPP and the Council of European Chief Dental Officers databanks. A literature search was then performed to access the reports of the studies that had produced these DMFT scores, cited on these databanks. The reports were then analysed to determine: the year in which the survey/study that produced the score took place, the year the results were published, the geographical area (national, regional or local) covered, the number of children examined, how many examiners took part, how they were trained and calibrated, and the criteria used for the detection of caries. Results: Data and information from 43 European countries were accessed. The years when the studies were performed ranged from 1990 to 2014. There were doubts over the representativeness of some samples. A wide range of different methods were used. Examiner training and calibration were very variable both in terms of duration and reported inter and intra-examiner consistency. There were important variations in the criteria employed for the detection of caries. Conclusions: These findings support the view that most of current national caries data for DMFT levels in 12-year-old children are not comparable across Europe. Key words: oral epidemiology, national mean DMFT, 12- year- old children, dental caries prevalence, variability, unreliability