A high-resolution pulse echo ultrasonic imaging system was developed to study decompression-induced gas bubbles. Such a system must be capable of detecting gas bubbles with a diameter of 10 .mu.m 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 .mu.m 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. The technique is extremely unlikely to induce any bubble formation by means of cavitation or thermal mechanisms. The system represents a powerful method for studying the factors controlling bubble formation.