Extracted premolars with an initial approximal caries were subjected to radiographic and histological examination. Radiographs were taken with the rectangular technique as used for bite-wing radiographs. Digital image processing was found to enhance the image information so that the border of caries lesions as well as histological structures, Retzius lines and Hunter Schreger stripes, within the body of the lesions were well defined. This helps to distinguish initial caries from depressions in the tooth surface.