Hidden occlusal caries was defined 20 years ago as a dentinal caries lesion near the occlusal surface of the tooth, visible on a radiograph, where in visual examination the occlusal enamel is seen intact or minimally perforated. Hidden caries present the dentist with challenges in prevention, diagnosis, treatment planning, patient education and research. This article describes these challenges and offers solutions. In trying to prevent the formation of hidden caries lesions, the dentist should consider using fissure sealants, which have already proved to be an efficient way of preventing fissure caries. Diagnosing hidden caries is a challenge for the dentist, who is used to detecting fissure caries solely by visual examination and probing, because, by definition, hidden caries should be diagnosed by radiographs. However, in order to diagnose occlusal carious lesions accurately, the practitioner must look for them on radiographs. In cases of inconclusive radiographic examinations and a stained fissure, an operative diagnosis approach should be employed. In treating hidden caries, the dentist should consider, according to clinical and radiographic examinations, an observation-only approach or a preventive resin restoration. The dentist should become familiar with this type of carious lesion and learn how to prevent, diagnose and treat it.