Hypoparathyroidism is an abnormality of calcium metabolism characterized by low serum levels of parathyroid hormone in spite of hypocalcemia. The causes of hypoparathyroidism are numerous. Activating mutations in the calcium-sensing receptor (CaSR) gene are well-known causes of familial isolated hypoparathyroidism, also known as autosomal dominant hypocalcemia (ADH). Here we describe members of a Korean family with a heterozygous Pro221Leu mutation causing ADH. This case is the first report in Korea.