Objective: The purpose of this in vivo study was to compare three different caries detection methods [laser fluorescence (LFE), visual examination (VE), and radiological examination (RE)] for the detection of occlusal caries in permanent posterior teeth. Background data: Early diagnosis of caries is critical in the management of dental caries. Methods: Two examiners assessed the occlusal surfaces of 217 teeth by visual, radiographic, and laser fluorescence (DIAGNOdent Pen) examination methods. After a 1 week interval, randomly selected patients were recalled. Each measurement was repeated by two examiners before the cases were selected for operative intervention to classify lesion depths. Statistical analysis of the data was performed using SPSS and Stata IC. The intra- and inter-examiner reliabilities and reproducibilities of the VE, RE, and LFE were calculated using Cohen's kappa statistics. The sensitivities and specificities were plotted in receiver operating characteristic curves. The differences between LFE scores were analyzed using the nonparametric Mann-Whitney U and Wilcoxon tests (alpha=0.05). Results: The VE method exhibited the highest sensitivity, accuracy, and kappa values among the diagnostic groups in terms of inter-examiner agreement. With regard to the sensitivity, specificity, and likelihood ratios for the two examiners, significant differences were found between sensitivity and specificity for examiner 1, whereas no statistically significant differences were noted between sensitivity and specificity for examiner 2 for the LFE scores. Conclusions: The DIAGNOdent pen is useful for the detection of dentinal caries of occlusal surfaces in permanent posterior teeth. Combination with other diagnostic conventional methods may enhance the reliability of this tool.