Oral ulcerations have very varied characteristics, the analysis of which is often sufficient for the clinician to establish a diagnosis and propose a suitable treatment. Aphthous ulcers and traumatic lesions are the most frequent, however one also sees infectious ulcerations (tuberculous, syphilitic, common germs or viruses), inflammatory diseases of the gastrointestinal tract, bullous dermatosis of autoimmune, toxic or unknown origin such as erythema multiform, and erosive lichen planus. It is thus the general context or the evolution that orientates the diagnosis, which is made more precise in certain cases by complementary investigations, in particular by the biopsy. When the ulceration is isolated it is necessary to first exclude the much-feared squamous cell carcinoma, but also other malignant ulcerated tumours, lymphomas, and tumours of the salivary glands. Thus it is imperative that the histological examination confirms the diagnosis, to formulate a prognosis and to allow the commencement of treatment.