No data about the prevalence of clinically undetected occlusal dentine caries are available in young German populations. Therefore the aim of this study was to determine the prevalence of clinically undetected occlusal dentine caries of first and second molars in 78 15-year-old German adolescents by occlusal judgement of bite-wing radiographs. The clinical observa-tions were collected as part of a longitudinal study of caries risk assessment conducted from 1993 to 1999. The same clinical criteria (WHO,1987) were used during the follow ups. Radio-graphic evaluation was only performed in 1999. Bite-wing radiographs were judged by 3 examiners, kappa 0.76. 5.6 D3MFS were clinically scored. 2.6 molars were sealed. After radiographic examination caries prevalence increased to 7.5 D3MFS. 1.8 D3-lesions were registered on the occlusal surfaces of the molars by clinical and radiographic judgements, while 1.3 D3-lesions were only radiographically detected. This difference was statistically significant (Mann-Whitney-Test: p 3S were found in sealed and in filled molars, respectively. 0.2 D3S were detected on clinically judged sound surfaces and 0.3 D3S in brown discoloured fissures. 11.1 % of all molars and 14 % of the sealed molars revealed a clinically undetected occlusal dentine caries. More than 70 % of all occlusal D3-lesions were exclusively detected by bite-wing radiographs. It can be concluded from this study that clinically undetected occlusal lesions are not only a problem in adolescents with low but also with high caries experience. Keywords: epidemiology, caries diagnostics, hidden caries, bitewing radiographs