Abstract Primary hyperparathyroidism is a common endocrine disease characterized by excessive secretion of parathyroid hormone from one or more of the four parathyroid glands. In most patients, a single, benign adenoma is responsible for the disease, but in a small percentage of subjects, four-gland hyperplasia is evident. Most patients present with sporadic disease but familial multiple endocrine gland syndromes are well known, with genetic bases that have been characterized. The clinical presentation of primary hyperparathyroidism has changed by virtue of the use of automated biochemical screening, in which the serum calcium is routinely measured as well as by a proactive approach to the investigation of known or suspected metabolic bone disease. As a result, three phenotypes of primary hyperparathyroidism are seen throughout the world. Symptomatic disease with skeletal and renal involvement is limited primarily to countries in which biochemical screening is not used and where vitamin D deficiency is endemic. Mild hypercalcaemia is the most common biochemical presentation in subjects who are discovered incidentally. The normocalcaemic variant of primary hyperparathyroidism is recognized in patients whose disease is manifest by elevated levels of parathyroid hormone in the absence of secondary causes. With recent advances in our ability to investigate in detail the two major target organs of primary hyperparathyroidism, namely bone and kidney, a more complete assessment of patients with this disease is now possible.