Intracellular fibrillar congophilic inclusions are well known as neurofibrillary tangles in neurons and as Biondi bodies in choroid plexus epithelial cells. Recently similar amyloid-like inclusions in adrenal cortical cells were described (Eriksson and Westermark 1990). This study on 150 adrenal glands confirms these observations. In our material the age-related accumulation of congophilic inclusions starts earlier (in the sixth decade) and reaches a higher incidence (42.7%). We found similar intracellular inclusions in other endocrine organs, for example in the anterior lobe of the pituitary, in the cells of parathyroid glands and in Sertoli cells. The age-related incidence of these fibrillar inclusions in the pituitary was 68%: the co-incidence with interstitial amyloid deposits was 49.5%. Thus the intracellular accumulation of congophilic fibrils in old age is a wide-spread phenomenon and occurs not only in neurons but also in endocrine cells (adrenal, pituitary and parathyroid glands) and in active secretory cells (choroid plexus and Sertoli cells).