This article, the third in a series, uses the tools described in the first 2 articles to examine some of the radiographic diagnostic procedures that are employed regularly in dental practice. With a general grounding in the meaning of terms such as sensitivity, specificity, thresholds, kappa coefficients, and predictive values, the reader should now be a more discerning user of the operating characteristic data for dental diagnostic procedures. By re-examining some of these procedures in terms of their effectiveness, accuracy and validity, dental practitioners should be able to use the procedures in a more targeted manner and gain the maximum benefit from their results. With a better understanding of the value of a diagnostic test, the clinician's decision-making process will be far better informed. For example, knowing that a certain radiographic view is associated with a 60% false-positive rate for identifying occlusal caries will preclude blind trust in the results and will help the informed clinician attribute a realistic weight to the radiographic findings. This article considers diagnostic procedures in common use in North American practice, with special emphasis on radiography.