The incidence of hypercalcemia in terminal cancer patients is rare but if it is not treated, the consequence is dismal. Hydration, diuretics, corticosteroids are not so effective for the treatment of hypercalcemia in this situation. Pamidronate (synthetic bisphosphonate analogue of pyrophosphonate) decreases the activity and the life span of the osteoclasts. It results in decrease in resorption of bone mineral, directly and indirectly. There are only a few reports on the usage of pamidronate in children. We experienced a case with hypercalcemia in patient with Wilms tumor who was treated with pamidronate. A 5-year-old male patient was admitted to Ajou University Hospital due huge abdominal mass. Abdominal CT revealed a huge mass originating from right kidney (size: 18 11 8 cm) with lung metastasis. The chemotherapy according to National Wilms Tumor Study (NWTS)-4 was started but there was no response after 4 months. Right nephrectomy with mass removal was done and the pathologic finding revealed diffuse anaplastic type. The serum calcium level increased to be 16.7 mg/dL at 7 days after operation which was not responsive to hydration and furosemide. Pamidronate was given at the dose of 1 mg/kg and the serum calcium decreased to 8.0 mg/dL 24 hours later. The pulmonary lesion progressed and the patient died 4 months after operation but the serum calcium level remained within normal range thereafter.