The diagnostic utility of intra-oral images obtained from the RVG second generation digital imaging system are compared with standard film images with the use of receiver operating characteristic analysis. Ten phantoms were constructed, each with 8 extracted teeth that had 12 approximal surfaces per phantom with holes drilled randomly to simulate approximal caries. Three images of each phantom were tested: a conventional film image, a thermal paper print, and a screen image. The images were rated by 26 dentists at separate sessions according to their confidence in the visibility of the simulated caries. A series of receiver operating characteristics curves were computed from the resulting 3120 decisions that indicate consistently greater success at detection of the holes on the film images. A full statistical analysis is given, and recommendations are made with respect to the use of this unit.