Abstract Micropipettes with ground beveled openings of 1 μ i.d. and smaller were utilized in a resistance servo-nulling pressure measuring system. The microcannulae, filled with 1 m NaCl have electrical impedance on the 8–11 Megohm range. The required bridge sensitivity was obtained with a negative capacitance input amplifier. In vitro frequency response is 25 Hz. In vivo tests in capillaries of the rabbit omentum showed pulsatile pressures.