Real-time 3D ultrasonic imaging requires a matrix of transducer elements with a number of elements that readily exceeds the number of channels of a conventional imaging system. This paper presents an ASIC, realized in a high-voltage 0.18 μm BCDMOS process, that interfaces a piezo-electric transducer array of 24 × 40 elements, directly integrated on top of the ASIC, to an imaging system using only 24 transmit and receive channels by means of a reconfigurable switch matrix and row-level low-noise amplifiers. Each element is associated with a compact bootstrapped high-voltage transmit/receive switch and programmable logic that enables a variety of imaging modes to be realized. The ASIC has been successfully used in a 3D imaging experiment.