Parathyroid hormone-related peptide (PTHrP, PLP) has previously been identified and assays are now available which can be used in clinical situations. A case is reported of a normocalcaemic young adult female in whom multifocal recurrent giant cell osteolytic lesions in the maxilla and elsewhere were associated with a raised plasma level of parathyroid hormone-related peptide. The lesions were histologically identical to reparative giant cell granuloma of the jaws and to osteitis fibrosa cystica associated with hyperparathyroidism.