The tongue is a movable, muscular organ important for many functions: taking food, chewing, swallowing, sucking, speech; and, as a sensory organ, it is important for taste and touch. Changes in the tongue can be physiological or pathological. The diseases of the tongue include: reactive and inflammatory processes such as hairy tongue, benign migratory glossitis, fissured tongue and pigmented fungiform papillae of the tongue; vascular and lymphatic lesions which include tongue varicosities and infantile haemangioma; infections which include candidiasis, hairy leukoplakia, infections caused by the herpes simplex virus, the varicella zoster virus, and human papillomavirus. The diseases of the tongue also include premalignant lesions such as leukoplakia and erythroplakia, as well as malignant lesions such as squamous-cell carcinoma of the tongue, Kaposi’s sarcoma, and lymphoproliferative disorders. Signs of systemic diseases such as immunodeficiencies, systemic amyloidosis, and taste sensitivity disorders are also indicated. There is a wide range of changes on the tongue. The patient can do a self-examination of the mucous of the tongue and the oral cavity, but they should be examined during every check-up visit of the patient.