Blood pressure is determined indirectly using a conventional cuff and electric pump for inflation. Cuff pressure is recorded by pressure transducers and oscillograph. The pulse-sensing mechanism is a fluid-filled balloon overlying the brachial artery. This is connected to a pressure transducer and a sensitive oscillographic galvanometer. Systolic and diastolic configurations are easily recognized and their respective pressures determined by referencing the calibrated curve of pressure within the cuff which is recorded simultaneously. This device, with modification, has been successfully used on the human centrifuge and high altitude chambers. Comparison of 90 automatic determinations on 10 subjects with simultaneous auscultatory measures produced a correlation coefficient of 0.97, with the former method showing the greater constancy. This validates the use of this indirect method for selected experimental situations. Submitted on August 5, 1955