Abstract: An ultrasonic scanning device having an ultrasonic transmission/reception probe arranged for rapid scanning in a plane while a housing of the device is being held stationary so that real time ultrasonic "pictures" of moving organs such as the heart, can be obtained. The probe is arranged to scan through a window of the housing and mounting means for the probe ensure that ultrasonic signals from the probe have a constant reference point of departure which is at a well-defined small distance from the window. Ultrasonic coupling means are provided between the probe and window, and the window, coupling means and probe may form a sub-assembly removable from the housing.