The skeletal lesions of primary hyperparathyroidism, including brown tumour, are rare nowadays, with the practice of checking serum calcium levels leading to an earlier diagnosis of hyperparathyroidism. Clinical, laboratory, radiographic and histological investigations can lead to a correct diagnosis. Treatment of brown tumour focuses on the hyperparathyroidism, and is usually followed by a regression of the brown tumour. The diagnosis of hyperparathyroidism and brown tumour should be considered in patients with hypercalcaemia and an osteolytic expansive bone lesion. We present a patient where a brown tumour of the mandible was the presenting symptom of primary hyperparathyroidism.