Aim of this investigation was to evaluate the validity and reproducibility of the universal visual scoring systems (UniViSS) on occlusal surfaces in vitro. The validity study included 65 third molars. Following to reach a UniViSS consensus diagnosis for each surface, all teeth were histologically prepared and evaluated according to the newly developed caries-extension-index (CE-index). The reproducibility study consisted of 149 molars. These teeth were examined by two dentists and four students without any calibration training. In result, the CE-index provided the exact caries depth for each UniViSS criterion, which could further be associated with a distinct preventive or treatment strategy. The mean intra-/inter-examiner weighted Kappa values amounted to 0.685/0.551 (UniViSS/severity) and 0.628/0.542 (UniViSS/discoloration). The cumulative Logit-model underlined that UniViSS/severity criteria were more frequently reproduced in comparison to the UniViSS/discoloration criteria. In conclusion, this study on the diagnostic performance of UniViSS showed encouraging results and give valuable hints for future studies.