A 24-hour, 3.5-lb., fully automatic, indirect blood pressure monitoring device has been developed that permits up to 40 programmed and manual readings each hour during normal daily activities. A study comparing the automatic ambulatory device with standard conventional sphygmomanometry revealed mean absolute differences of blood pressure measurement of less than 5 mmHg and mean pairwise differences of 2 mmHg for both systolic and diastolic pressures.