This report deals with a case of atypical histiocytic granuloma in a male patient of 65 years old. The white ulcerative lesion was located in the upper labial mucosa. No bleeding or pain was observed on palpation. A complete spontaneous healing was observed within two weeks. On histologic examination an excess of atypical cells with multiple mitotic configurations was seen. These cells were histiocytes (this was substantiated by the use of a specific histochemical colour method (KP1-CD 68)). The authors emphasize the difficult clinical differential diagnosis with a traumatic eosinophilic granuloma. Also the other ulcerative lesions, including spinocellular epithelioma, of the oral mucosa must be considered. Only biopsy will differentiate between these entities.