Accurate diagnosis of the presence or absence of disease is a fundamental requirement in health care. The diagnosis of non-overt occlusal decay is challenging and can be highly subjective, and lead to widely differing treatment decision. The development of more sensitive and reproducible diagnostic tools for occlusal surfaces would contribute greatly to more precise planning of preventive and operative. Conventional visual, tactile, and radiographic examinations provide less than ideal diagnostic sensitivity. Neither fissure discoloration nor the use of an explorer has been shown to improve diagnostic accuracy. However, the combination of careful visual examination with optical radiographic examination affords better diagnostics performance. The best visual indicators involve precise features associated with presence of disease, Such as opaque fissure demineralization and the presence and extent of localized breakdown of the enamel. For best results teeth should be clean, thoroughly dry and well illuminated. New and emerging technologies, including the DIAGNOdent laser fluorescence device, are being developed for the diagnosis of occlusal decay.