The autoregulation theory of hypertension has been attractive because it postulates a mechanism whereby an early rise in cardiac output becomes "transformed" through normal autoregulatory processes into an elevated total peripheral resistance. 2. "Normal" autoregulation involved in control of blood flow of regional beds is a rapid process compared with the slow changes postulated by the autoregulation theory. 3. Evidence is presented that under appropriate experimental conditions " volume" factors (cardiac output) and "constrictor" factors exert independent long-term effects in developing and in established hypertension. There is little evidence to support the autoregulation theory of hypertension.
