The current state of art of medical ultrasonotomography is briefly reviewed. The ultrasonic characteristics of living tissues are briefly summarizedand the instrumentation for B-mode imaging is described with an emphasis on electronic scanning system. The other ultrasonic imaging systems such as ultrasonic computerized tomography and ultrasonic holography are also briefly described andthe inherent problems of these systems are pointed out. Towards the future goal, discussion is presented on the possibility of solving general “inverse problem”, that is, estimating spatial distribution of all ultrasonic parameters inside the body from the observation outside.
