Metastasis of a tumour to the mandibular condyle is rare. We describe a case in which a patient presented with isolated condylar metastasis mimicking acute internal derangement of the temporomandibular joint (TMJ). Open biopsy revealed a lesion seated within the condylar head and extending through the bony cortex to the infratemporal fossa. Histopathology confirmed the diagnosis of metastatic large-cell lung carcinoma. TMJ dysfunction may be associated with any pathologic entity involving the mandibular condyle. A panoramic radiograph should be considered in patients who do not respond to conventional therapy or whose clinical symptoms worsen. Particular attention must be paid to osteolytic jaw lesions, which can be the "tip of the iceberg" indicating widespread metastatic disease.