An high-resolution pulse echo ultrasonic imaging system has been developed to study decompression-induced gas bubbles. It was considered necessary that the system be capable of detecting gas bubbles with a diameter of 10 micrometer and up and be able to monitor the growth of these bubbles. In addition the system needed to be capable of distinguishing separate gas bubbles from within an area containing a number of bubbles and allowing their position to be accurately located. The current system is capable of detecting bubbles as small as 10 micrometer and of resolving bubbles separated by 0.8 mm in azimuth and 0.4 mm in range, and these values correspond to the maximum accuracy of location. Finally, it has been shown that the technique is extremely unlikely to induce any bubble formation by means of cavitation or thermal mechanisms. It is concluded that the system represents a powerful method for studying the factors controlling bubble formation.