The clinical phenotype of primary hyperparathyroidism in the United States has changed markedly over the past century, with the majority of patients having minimal overt symptomatology. It has become clear, however, that "asymptomatic" primary hyperparathyroidism is a disease with distinct physiologic characteristics. Data accumulated over recent years suggest that asymptomatic patients meeting specific criteria can be safely followed without surgery. These guidelines are elucidated, and new options in the medical therapeutics of primary hyperparathyroidism are discussed.