A group of seven children with different malignant processes presenting with hypercalcemia was studied. Bone destruction, diffuse metabolic abnormalities, abnormal acid-base homeostasis and recurrent hypercalcemia characterized these patients. A different mechanism leading to the production of hypercalcemia and/or bone destruction by cancer cells is considered. The results of this report suggest that parathyroid hormone production (P.T.H.) by the parathyroid glands is normal and that ectopic secretion of PTH or PTH-like material is negligible in these cases.