The circulation around a closed path encompassing the primary vortex of stationary delta wings has been investigated through the use of a novel ultrasound technique. Ultrasonic pulses propagating in clockwise and counterclockwise directions enclosed a fixed path that was positioned perpendicular to the delta-wing root chord line. Circulation in the plane of the closed path then was determined from the transit-time difference between the clockwise and counterclockwise pulses. Half-delta wings with sweep angles of 60 and 70 deg were tested over a range of angles of attack up to 38 and 52 deg, respectively, and at chordwise distances of 35, 50, 65, and 80% from the wing apexes. Circulation increased monotonically with angle of attack for both sweep angles until it reached a maximum value, beyond which the total circulation decreased or remained nearly constant. The angle of attack associated with the maximum circulation is correlated with conditions resulting in feeding sheet interaction on the symmetry plane. At any angle of attack, circulation increased approximately linearly with increasing chordwise location as long as the feeding-sheet interaction was not present