We report the kindred with familial isolated hyperparathyroidism with parathyroid cancer. The proband was diagnosed as having primary hyperparathyroidism at age 43. The same disorder was also found in his daughter who had low bone mass. His son was found to have primary hyperparathyroidism by family screening. The pathological diagnosis of the resected parathyroid in both father and daughter was parathyroid cancer, and that in son was parathyroid adenoma. The right lower gland of the proband and the left lower gland of the son were present in thymus. No mutations were found in the sequences of MEN1 gene, hence gene(s) other than MEN1 gene may have contributed to the malignant potency in our cases.