Objective: To evaluate the diagnostic efficacy of the bitewing radiograph(BWR),clinic examination(CE) and laser fluorescence examination (LF) for detection of initial posterior approximal caries . Methods:A total of 162 approximal surfaces from 81 extracted posterior teeth were examined by BWR, CE and LF. The histological diagnosis of sectioned teeth was used as the validating criterion (gold standard) to assess the sensitivity, specificity, accuracy and reproducibility. Results: The sensitivity and accuracy of BWR was higher than those of CE or LF at the level of enamel caries. Conclusions: BWR is an accurate diagnostic method for initial posterior approximal caries in present clinic practice. The inferior efficacy of LF is mainly due to its poor reproducibility of approximal surfaces.