To review the history and application of laboratory assays for the measurement of parathyroid hormone.Perinent literature documenting the development of the parathyroid hormone assay was reviewed.Following its introduction in 1963, the parathyroid hormone assay has evolved into a highly sensitive and specific test. It is now a rapid (less than 20 minutes), relatively inexpensive modality that can be performed without the use of radioactive isotopes. However, the assays commonly used today in clinical practice are still susceptible to certain types of interference and artifact.In-house measurement of parathyroid hormone, as well as intraoperative parathyroid hormone monitoring, is now widely available to clinicians in most larger hospitals. This accessibility has greatly facilitated the study and understanding of primary hyperparathyroidism. Despite assay improvements, the measurement of parathyroid hormone in patients with renal disease remains problematic.