The detailed ultrastructural changes of uremia-induced hyperplastic parathyroid gland and the effects of current medical treatments for secondary hyperparathyroidism were investigated. Marked enlargement of parathyroid cell with accumulation of mitochondria and lipids and a significant increase in the thickness of the pericapillary area with increased fibrosis and appearance of fibroblast like cells were noted in the hyperplastic gland caused by uremia and phosphate retention. These ultrastructural changes and biochemical findings indicating hyperparathyroidism were significantly suppressed by all of the treatment using phosphate restriction, calcitriol, and cinacalcet. The characteristic ultrastructural changes, including the morphologic evidence of nodule formation, were indicated.