An 81-year-old man had left labial paresthesia and a palpable mass adjacent to the left mental foramen 6 months after apparent adequate excision of a small (1.5 cm) primary squamous cell carcinoma of the left portion of the lower lip. Biopsy and clinical evaluation revealed recurrent squamous cell carcinoma. Subsequent left hemimandibulectomy confirmed perineural extension of tumor along the mandibular branch of the trigeminal nerve to the foramen ovale. Seven months later, the patient died of complications resulting from intracranial extension of tumor to the left cerebellopontine angle. This case illustrates the lethal potential of carcinoma of the lip due to contiguous perineural extension, even with a small primary tumor and absence of regional lymph node metastases.