A non-invasive apparatus and method for monitoring the blood pressure of a subject detects a pulse signal at both a first and second location on the subject's body The elapsed time between the arrival of corresponding points of the pulse signal at the first and second locations is determined. Blood pressure is related to the elapsed time by relationships such as: P=a+b ln(T), where a and b are constants dependent upon the nature of the subject and the signal detecting devices. The system can be calibrated by measuring a single pair of reference blood pressure and corresponding elapsed time