Lymphomatoid papulosis (LyP) may involve any cutaneous site but the oral areas seems to be an unusual location. We report a 72-year-old patient who presented with a 1-week history of a solitary oral ulcer on the lateral tongue, which had raised and indurated borders. Although squamous cell carcinoma was initially diagnosed, the morphological, phenotypical and genotypical studies confirmed diagnosis of LyP. We are not aware of previous reports of definite LyP presenting as oral lesions, which may pose a diagnostic challenge. The differential diagnosis includes several neoplastic, reactive and infectious disorders. LyP should be considered in patients showing solitary, rapidly developing ulcers with raised, indurated borders in the oral cavity. © 2009 British Association of Dermatologists.