The robustness of a relationship among physical fitness, psychomotor speed, and aging is discussed by reviewing the descriptive and correlational evidence provided by studies from several different research areas. These areas are those that relate psychomotor speed to (a) athletic status, (b) physical fitness status, (c) physical conditioning training programs, (d) hyperbaric oxygenation treatment, and (e) presence of cardiovascular disease. Several potential physiological mechanisms that might support such a relationship are discussed under the general categories of brain function and cerebral circulation, and the trophic influence of physical activity on the central nervous system.