In this Part 2, pharmacodynamic studies which have examined the possibility of true changes in drug "sensitivity" in old age are reviewed. In a variety of organ systems, age-related physiological changes are reflected in altered drug responsiveness in the elderly. Also, a better understanding of different pathophysiological background of disease in this age group leads to a more rational pharmacotherapeutic approach, which is exemplified in the recent drug therapy of hypertension in the elderly.