Abstract: The rate of change in a selected portion of an arterial pressure pulse changes with applied constricting pressure, and the pattern of the change undergoes a progressive transition at a value of constricting pressure that is offset by a fixed amount below the true diastolic value. Diastolic pressure measurement based on this transition examines the rate of change of the arterial pressure pulse as the constricting pressure changes over a range of sub-diastolic values, determines the occurrence of the transition, and identifies the applied pressure at which the transition occurs. The offset pressure is added to the determined value of applied pressure to yield the desired measure of diastolic pressure.