Authors examined the peripheral lymphocytes of 366 healthy individuals electron microscopically. They described age related degenerative changes in the mitochondria. The lamellar structure, electron-dense and electron-opaque material shown in the mitochondria of the lymphocyte proved to be similar to lipofuscin. The relationship of mitochondrial damage in lymphocytes and age was analysed, too. They stated that the number of patients with mitochondrial changes in the lymphocytes increased from 50 years of age until 80 years, but after 80 years decreased.