Parathyroid adenomas are classified into two types: chief cell and oxyphil cell variants. In this report two types of parathyroid adenoma in association with hyperparathyroidism were examined. Both cases had suffered from renal calculi, and underwent operation. The laboratory tests showed high serum calcium and parathyroid hormone (PTH) levels. An exploratory surgery revealed a solitary tumor in each case. After extirpation of the parathyroid tumor these data returned to normal values. Electronmicroscopically, oxyphil cell adenoma in this report was characterized by numerous mitochondria and annulate lamellae in the cytoplasm. In some tumor cells secretory-like granules were observed.