Parathyroid hormone-like peptide (PLP) is produced by a number of tumors commonly associated with hypercalcemia as well as by nontumorous tissue, including some endocrine organs. We applied immunohistochemistry using the avidin-biotin-peroxidase technique to localize PLP in formalin-fixed, paraffin-embedded tissues of two human pancreatic carcinomas associated with hypercalcemia and normal blood parathyroid hormone levels. One tumor was endocrine and one was exocrine in differentiation. There was no evidence of bone metastasis in either case. We documented normalization of serum calcium level after removal of the pancreatic endocrine tumor. These observations support the suggestion that PLP production by pancreatic carcinoma may play a role in the development of hypercalcemia. However, the presence of PLP in tumors not associated with hypercalcemia indicates that other factors in addition to PLP are necessary for the manifestation of hypercalcemia. Hypercalcemia associated with exocrine pancreatic tumor has rarely been reported. Our exocrine pancreatic tumor appears to be the first reported case in which immunohistochemistry localized PLP. Since PLP has been localized to cells of exocrine ducts and ductules of normal pancreas, our results provide insight into the cell of origin of this tumor type.