Abstract: An improvement to ultrasonic probes useful in the non-destructive testing of structural materials includes a compact, high-sensitivity coaxial design probe. The probe has a centrally located transmitter point and a circumferentially arranged receiver ring. The geometrical relationship between the transmitter point and the receiver ring provides for high-sensitivity in the detection of defects and allows for a compact construction without orientational sensitivity. A receiver tube is provided which encloses the probe and acts as a tuned wave guide for the detection of ultrasonic vibrations from the structural material under test. The increased sensitivity of the improved ultrasonic probe is advantageous in the testing of non-metallic structural materials having a complex composite structure. The compactness of the improved ultrasonic probe is advantageous in the testing of structural materials having complex and narrow shapes.