Hyperparathyroidism-jaw tumour (HPT-JT) syndrome is characterized by parathyroid tumours as well as by ossifying fibromas of the mandible and maxilla, renal cysts, or Wilms' tumours. Recently, the gene responsible for HPT-JT syndrome has been identified as the HRPT2 tumour suppressor gene. In an 18-year-old male, a tumour in the maxilla was first diagnosed as an ossifying fibroma. During biochemical screening before surgery, the patient received a diagnosis of primary hyperparathyroidism. Neck computed tomography scanning showed a parathyroid tumour. Surgical excisions to remove the jaw tumour and parathyroid adenoma were performed. The postoperative course has been uneventful and a follow up at 2 years revealed no evidence of recurrence. The HRPT2 germline mutation of 39delC was detected in the proband, but not in his unaffected parents. These results suggested that the germline mutation occurred de novo.