The application of ultrasonics to medical diagnostic method has not been so much successful, because the complexity of the sound reflecting structures echos which are so numerous and variable that controlled experiments and consistent results are difficult to obtain. In this point, fundamental electrical and ultrasonic study in medicine has been very important; electrical circuit of the pulse generater, receiver, amplifier and indicator, pulse length and intensity of the transmitter, the directibility of the ultrasonic beam and scanning mehtod, they would be concerned with upper problem. A new type of apparatus for this study has been designed and produced by the author; Sensitivity of the recciver is 90～100 dB, measuring distance is 2mm～1.8m and the freguency of the pulse generator is 0.5MC～10MC. A 500pF capactior is charged to about 1,800 V through a high resistance and is then discharged by a thyratron tube (3C45) through the primary winding of a pulse transformer. The amplitude of the transmited ultrasonic pulse rises from lμs to its maximum value in 20μs. Fifty or sixty such pulses are transmited each secound to human body. This apparatus has been used to diagnostic medicine and fundamental study in the author's clinic.