Ultrasonic phased array method and apparatus for the static or dynamic investigation of structures, such as organs of the body, or intra-uterine detail, wherein ultrasonic echo pulses, reflected back from a testpiece to one or a group of adjacent transducers of a linear transducer array, are converted to corresponding electric signals which are then processed to maximize the response to the echo pulses reflected from points on a predetermined axis and to minimize the response to all other echo pulses. The method is repeated using another group of transducers in the array and another predetermined axis to produce fields of video information which are focussed and then interlaced to provide an image of the testpiece at a particular instance, the method steps being repeated in rapid succession to provide a video image representative of the testpiece in real time.