The labial mucosa is an unusual site for basal cell carcinoma. Only a few cases have been reported in the literature. We present a case of basal cell carcinoma wich involved the vermilion of the lower lip. A 77-year-old man presented with an ulcer taking half of his lower lip and extending to the skin evolving for two years. There were no cervical lymph nodes. Diagnosis of infiltrative basal cell carcinoma was made by histological study which showed a tumoral proliferation starting from epidermal basal layers infiltrating the hypodermis with perineural infiltration. The pathogenesis of basal cell carcinoma of the vermilion lip is not clear. While basal cell carcinoma originates from pilar structures, the lack of pilosebaceous follicles in the normal lip mucosa has led to several hypotheses to explain the pathogenesis of mucosal basal cell carcinoma. Our case shows a very rare location of basal cell carcinoma. The ulcer that originally started in the vermilon, has extended and reached the mucosa and the skin areas. Therefore, basal cell carcinoma should be considered among the differential diagnosis of ulcerative lesions of the lip