Pituitaries obtained at autopsy from 18 men and 17 women, over 80 years of age, who died of various acute illnesses, were investigated histologically by various staining procedures, including the immunoperoxidase technique. Compared with pituitaries of 10 male and 10 female subjects who died of short-lasting diseases between 20 and 56 years of age, no involution of growth hormone cells was found in pituitaries of the older group. Incidence, distribution, granulation and immunoreactivity of growth hormone cells showed no apparent difference related to age and sex. Lack of regression of growth hormone cells with advancing age indicates that the pituitary can produce growth hormone in old subjects.