Intraoral radiographs are widely used in periodontal diagnosis and research. However, accurate radiographic interpretation is only possible with high quality images. Some of the technical and geometric variables to consider have been presented. Early periodontal lesions are not detected in radiographs. The amount of periodontal destruction in more advanced disease is generally underestimated. The accurate topography of periodontal pockets and the buccal and lingual aspects of the teeth cannot be visualized. Clinical probing is therefore a prerequisite for a complete periodontal diagnosis. However, radiographs are a valuable adjunct for the periodontal diagnosis and the diagnosis of trauma from occlusion. With standardized systems, radiographs may furnish additional quantitative data in clinical research.