This is part 6 of a 10-part series entitled Caries Process and Prevention Strategies. This course introduces the dental professional to the importance of caries diagnosis in prevention of the disease, as well as the intricate link between caries diagnosis and treatment. The two main methods of lesion diagnosis used today-the visual-tactile or visual methods and bitewing radiography-are discussed, including recent advancements that improve their sensitivity, as well as their limitations. Topics also include newer approaches to caries diagnosis and management, a brief discussion of why too-early caries lesion diagnosis can be counterproductive and the benefits of enlisting the help of pediatricians in diagnosing caries in children.