This pater present a case of primary hyperparathyroidism associated with the pathologic fracture of femur at the Korea University Hospital. A 55-years old housewife had complained of pain on left thigh with weakness, nausea and constipation for three months and was admitted due to the fracture of left femyr. The laboratory findings were revealed hepercalcemia, hypophosphatemia, increased alkaline phosphatase and parathyroid hormone. The simple X-ray findings of left femur revealed the irregular osteolytic change, the thinning of the cortex and transverse fracture in midshaft of Lt. femur Sonogram and CT of the neck revealed a mass in the left upper portion of the thyroid. After parathyroidectomy and intramedullary nailing with bone graft, the clinical symptom and abnormal laboratory findings were recovered to normal. So authors report a case of primary hyperparathyroidism associated with pathologic fracture of left femur.