Aim of this study was to assess the reliability of the measurement of occlusal caries by a laser fluorescent technique. Four dentists using four DIAGNOdent® devices (Dd) according to manufacturers instructions examined 80 carefully cleaned molars with non-cavitated occlusal lesions. Inter- and intra-examiner reproducibility were calculated using Lin's intra-class correlation coefficient (ICCLin), Students t-test and the limits of agreement by Bland and Altman (1990). Excellent intra-examiner reproducibility was found for dentist 2 and dentist 4. Significant differences were calculated for dentist 1 and dentist 3. Inter-examiner reproducibility was significantly different between dentist 3 and each of the other dentists. Significant differences between Dd instruments disappeared after exclusion of all readings of dentist 3. Categorising Dd values in order of treatment related cut-offs a substantial reproducibility was found in the range of 0-14 (ICCLin 0.66) and >30 (ICCLin 0.65). Only 41.6% of all Dd measurements were reproduced in the range 15-30 (ICCLin 0.16). The results suggest that dentists should be trained before using Dds. The low reliability in the interval of 15-30 could limit the use of Dds for a longitudinal caries monitoring on occlusal surfaces. Keywords: DIAGNOdent, Laserfluoreszenz-Messung, Kariesdiagnostik, Reproduzierbarkeit, Variabilität