The complication of hypercalcemia is reported to occur only in 2.5–4.8% of patients with acute lymphoblastic leukemia (ALL). We herein report a 53-year-old female patient with early B-cell ALL, complicated with extreme hypercalcemia (15.2 mg/dL). Bone X-ray revealed osteolytic changes in many locations. Serum 1,25(OH)2vitaminD3and parathyroid hormone(PTH) levels were suppressed below normal ranges on admission. The circulating parathyroid hormone-related protein (PTHrP) value was within a normal range (< 1.1 pmol/L). Serum concentrations of tumor necrosis factor (TNF)-&agr;, interleukin (IL)-6, and soluble IL-2 receptor were increased to 72 pg/ml, 25.3 pg/ml, and 1469 U/ml, respectively. Following the induction chemotherapy, the serum calcium level was promptly normalized accompanied with decreases in serum TNF-&agr;, IL-6 and soluble IL-2 receptor values to 34 pg/ml, 6.35 pg/ml, and 737 U/ml, respectively. Serum PTHrP values remained within detectable levels. To our knowledge, this is the first case of B-cell ALL in a patient who developed hypercalcemia with elevated concentrations of TNF-&agr;, IL-6, and soluble IL-2 receptor, but not related to PTHrP. High circulating proinflammatory cytokines may have contributed to development of ALL-induced osteolysis and hypercalcemia in the present case.