More surgeons are performing unilateral exploration for primary hyperparathyroidism (HPT) than ever before. This article reviews the factors that have led to the trend toward less invasive surgery. Discussion includes the history of unilateral exploration for HPT, the advent of magnetic resonance sestamibi imaging, and the development of intraoperative assays for parathyroid hormone. Results of minimally invasive techniques, including radio-guided parathyroidectomy, endoscopic parathyroidectomy, and outpatient parathyroidectomy, also are presented.